Orientalium ecclesiarum or the Decree on the Eastern Catholic Churches of November 21, 1964 presents the diaconate in a somewhat different perspective than Lumen gentium No 29. The reader is asked to reflect on the text including the footnotes. There will appear a commentary in the near future.

(St. Roman, the Sweet Singer)
17. In order that the ancient established practice of the sacrament of orders in the eastern churches may flourish again, this sacred council ardently desires that the office of the permanent diaconate should, where it has fallen into disuse, be restored.(21) The legislative authorities of each individual church should decide about the subdiaconate and the minor orders and the rights and obligations that attach to them.(22)
Footnote 21 (Note that this footnote refers to six separate sources. Orientalium ecclesiarum does not provide the actual texts. They are provides below for the convenience of the reader.)
(1) Nicaea I, canon 18. AD 325
It has come to the attention of this holy and great synod that in some places and cities deacons give communion to presbyters, although neither canon nor custom allows this, namely that those who have no authority to offer should give the body of Christ to those who do offer. Moreover it has become known that some of the deacons now receive the Eucharist even before the bishops. All these practices must be suppressed. Deacons must remain within their own limits, knowing that they are the ministers of the bishop and subordinate to the presbyters. Let them receive the Eucharist according to their order after the presbyters from the hands of the bishop or the presbyter. Nor shall permission be given for the deacons to sit among the presbyters, for such an arrangement is contrary to the canon and to rank. If anyone refuses to comply even after these decrees, he is to be suspended from the diaconate.
(2) Synod of Neocaesarea, canon 12, AD 314-325
If any one be baptized when he is ill, forasmuch as his [profession of] faith was not voluntary, but of necessity [i.e. though fear of death] he cannot be promoted to the presbyterate, unless on account of his subsequent [display of] zeal and faith, and because of a lack of men.
(3) Synod of Sardica, canon 8, AD 343
Greek: Bishop Hosius said: This also let your sagacity determine, that — inasmuch as this was decreed in order that a bishop might not fall under censure by going to the Court— that if any have such petitions as we mentioned above, they should send these by one of their deacons. For the person of a subordinate does not excite jealousy, and what shall be granted [by the Emperor] can thus be reported more quickly. All answered: Be this also decreed.
Latin: Bishop Hosius said: This also your forethought should provide for— inasmuch as you have made this decree in order that the audacity of bishops might not labour [or, be observed] to go to Court. Whosoever therefore shall have or receive petitions such as we have mentioned above, let them send these [each] by a deacon of his, because the person of a minister is not an object of jealousy, and he will be able to report more quickly what he has obtained.
(4) Leo the Great, letter Omnium quidem, 13 Jan. 444. LETTER VI. To Anastasius, bishop of Thessalonica.
Leo to his beloved brother Anastasius.
I. He is pleased to have been consulted by the bishops of Illyricum on important questions.
The brotherly love of our colleagues makes us read with grateful mind the letters of all priests; for in them we embrace one another in the spirit as if we were face to face, and by the intercourse of such epistles we are associated in mutual converse. But in this present letter the affection displayed seems to us greater than usual: for it informs us of the state of the churches, and urges us to a vigilant exercise of care by a consideration of our office, so that being placed, as it were, on a watch-tower, according to the will of the Lord, we should both lend our approval to things when they run in accordance with our wishes, and correct, by applying the remedies of compulsion, what we observe gone wrong through any aggression: hoping that abundant fruit will be the result of our sowing the seed, if we do not allow those things to increase which have begun to spring up to the spoiling of the harvest.
II. Following the examples of his predecessors he nominates Anastasius metropolitan of Illyricum.
Now therefore, dear brother, that your request has been made known to us through our son Nicolaus the priest, that you, too, like your predecessors, might receive from us in our turn authority over Illyricum for the observance of the rules, we give our consent and earnestly exhort that no concealment and no negligence may be allowed in the management of the churches situated throughout Illyricum, which we commit to you in our stead, following the precedent of Siricius of blessed remembrance, who then, for the first time, acting on a fixed method, entrusted them to your last predecessor but one, Anysius of holy memory, who had at the time well deserved of the Apostolic See, and was approved by after events: that he might render assistance to the churches situated in that province whom he wished kept up to discipline. Noble precedents must be followed with eagerness that we may show ourselves in all things like those whose privileges we wish to enjoy. We wish you to imitate your last predecessor but one as well as of your immediate predecessor who is known equally with the former to have both deserved and employed this privilege: so that we may rejoice in the progress of the churches which we commit to you in our stead. For as the conduct of matters progresses creditably when committed to one who acts well and carries out skillfully the duties of the priestly position, so it is found to be only a burden to him who, when power is entrusted to him, uses not the moderation that is due.
III. Ordinees must be carefully selected with especial reference to the canons of the church.
And so, dear brother, hold with vigilance the helm entrusted to you, and direct your mind's gaze around on all which you see put in your charge, guarding what will conduce to your reward and resisting those who strive to upset the discipline of the canons. The sanction of God's law must be respected, and the decrees of the canons should be more especially kept. Throughout the provinces committed to thee let such priests be consecrated to the Lord as are commended only by their deserving life and position among the clergy. Permit no licence to personal favour, nor to canvassing, nor to purchased votes. Let the cases of those who are to be ordained be investigated carefully and let them be trained in the discipline of the Church through a considerable period of their life. But if all the requirements of the holy fathers are found in them, and if they have observed all that we read the blessed Apostle Paul to have enjoined on such, viz., that he be the husband of one wife, and that she was a virgin when he married her, as the authority of God’s law requires,[then ordain them]. And this we are extremely anxious should be observed, so as to do away with all place for excuses, lest any one should believe himself able to attain to the priesthood who has taken a wife before he obtained the grace of Christ, and on her decease joined himself to another after baptism. Seeing that the former wife cannot be ignored, nor the previous marriage put out of the reckoning, and that he is as much the father of the children whom he begot by that wife before baptism as he is of those whom he is known to have begotten by the second after baptism. For as sins and things which are known to be unlawful are washed away in the font of baptism, so what are allowed or lawful are not done away.
IV. The metropolitans must not ordain hastily nor without consulting their primate.
Let no one be ordained a priest throughout these churches inconsiderately; for by this means ripe judgments will be formed about those to be elected, if your scrutiny, brother, is dreaded. But let any bishop who, contrary to our command, is ordained by his metropolitan without your knowledge, know that he has no assured position with us, and that those who have taken on themselves so to do must render an account of their presumption. But as to each metropolitan is committed such power that he has the right of ordaining in his province, so we wish those metropolitans to be ordained, but not without ripe and well-considered judgment. For although it is seemly that all who are consecrated priests should be approved and well-pleasing to God, yet we wish those to have peculiar excellence whom we know are going to preside over the fellow-priests who are assigned to them. And we admonish you, beloved, to see to this the more diligently and carefully, that you may be proved to keep that precept of the Apostles which runs, "lay hands suddenly on no man."
V. Points which cannot be settled at the provincial synod are to be referred to Rome.
Any of the brethren who has been summoned to a synod should attend and not deny himself to the holy congregation: for there especially he should know that what will conduce to the good discipline of the church must be settled. For all faults will be better avoided if more frequent conferences take place between the priests of the Lord, and intimate association is the greatest help alike to improvement and to brotherly love. There, if any questions arise, under the Lord’s guidance they will be able to be determined, so that no bad feeling remains, and only a firmer love exists among the brethren. But if any more important questions spring up, such as cannot be settled there under your presidency, brother, send your report and consult us, so that we may write back under the revelation of the Lord, of whose mercy it is that we can do ought, because He has breathed favourably upon us: that by our decision we may vindicate our right of cognizance in accordance with old-established tradition and the respect that is due to the Apostolic See: for as we wish you to exercise your authority in our stead, so we reserve to ourselves points which cannot be decided on the spot and persons who have made appeal to us.
VI. Priests and deacons may not be ordained on weekdays any more than bishops.
You shall take order that this letter reach the knowledge of all the brethren, so that no one hereafter find an opportunity to excuse himself through ignorance in observing these things which we command. We have directed our letter of admonition to the metropolitans themselves also of the several provinces, that they may know that they must obey the Apostolic injunctions, and that they obey us in beginning to obey you, brother, our delegate according to what we have written. We hear, indeed, and we cannot pass it over in silence, that only bishops are ordained by certain brethren on Sundays only; but presbyters and deacons, whose consecration should be equally solemn, receive the dignity of the priestly office indiscriminately on any day, which is a reprehensible practice contrary to the canons and tradition of the fathers, since the custom ought by all means to be kept by those who have received it with respect to all the sacred orders: so that after a proper lapse of time he who is to be ordained a priest or deacon may be advanced through all the ranks of the clerical office, and thus a man may have time to learn that of which he himself also is one day to be a teacher.
Dated the 12th of January, in the consulship of Theodosius (18th time) and Albinus(444).
(Please note the discrepancy in the dating of the letter by one day.)

(St. Lawrence the Martyr)
(5) Chalcedon, canon 6, AD 451
No one, whether presbyter or deacon or anyone at all who belongs to the ecclesiastical order, is to be ordained without title, unless the one ordained is specially assigned to a city or village church or to a martyr’s shine or a monastery. The sacred synod has decreed that the ordination of those ordained without title is null, and that they cannot operate anywhere, because of the presumption of the one who ordained them.
(6) Constantinople IV, canon 23 AD 869-870
We have also learnt that some bishops, at the request of certain people, have unreasonably made a gift of properties belonging to other churches. Thus they usurp the authority of other bishops, so far as they can. This conduct will clearly bring on them the curse of the prophet who says, Woe to those who add house to house and field to field (Is 5:8) in order to defraud their neighbor, and it has made them guilty of sacrilege. For this reason this great and universal synod had decided that no brother of ours in the episcopate or anyone else may transact such a wicked property deal, nor, if asked by someone dispose of any property belonging to other churches, nor install priests or any other clerics in churches that are not under his jurisdiction, without the permission of the bishop responsible for the church in question. Furthermore, no priests or deacons, who are consecrated for holy functions, should perform, of their own accord and decision, any sacred functions in churches to which they have not been appointed from the beginning. This behavior is unlawful and utterly alien to the canonical regulations.
Whoever, after this declaration of ours, shall be seen to do any of these things which have now been forbidden, must be excommunicated for a period of time, and the contractual arrangements, whether written or not, must be completely dissolved and abrogated because they were made in contravention of the canons. Likewise, the priest or deacon is to be suspended until he withdraws from the church to which he does not belong. But if he ignores the suspension, he must be got rid of completely and dispossessed of every sacred office.
Canon 26
This holy synod has also decided that any priest or deacon who has been disposed by his bishop for some crime, or who alleges he has suffered some kind of injustice and is not satisfied with the judgment of his bishop, saying that he does not trust him and that he has been wronged, either because of the enmity which the bishop has for him or because of favours the bishop wants to bestow on certain others, such a person has the right to have recourse to the metropolitan of his province and to denounce his deposition from office, which he thinks is unjust, or any other injury. The metropolitan should be willing to take up such cases and to summon the bishop who has deposed the cleric or injured him in any way. He should examine the case himself, with the help or other bishops, so as either to confirm the deposition of the cleric beyond all doubt, or to quash it by means of a general synod and the judgment of many persons.
In the same way we decree that bishops may have recourse to the patriarch, their head, if they complain that they have suffered similar things from their metropolitan, so that the business in question may receive a just and right decision from their patriarch and the metropolitans under him. No metropolitan bishop may be judged by his neighbouring metropolitan bishops, even though it is alleged that he has committed serious crimes, but he may only be judged by his own patriarch; we decree that this judgment will be just and beyond suspicion because a number of esteemed people will be gathered around the patriarch, and for this reason his judgment will be fully ratified and confirmed. If anyone does not agree with what we have promulgated, let him be excommunicated.

(Protodeacon Alexander Ageikin)
Footnote 22: In many eastern churches the subdiaconate is regarded as a minor order; but in Pius XII’s Motu proprio Cleri sanctitati the obligations of the major orders were prescribed for it. The present canon proposes a return to the ancient rule of each church as regards the obligations of subdeacons, in derogation of the common law of Cleri sanctitati.