Lumen Gentium affirms the councils view of the hierarchy by delineation; It declines to mention minor orders, including the subdiaconate, and further, explicitly lists only bishops, and their assistants priests and deacons, as holding sacred ministry. (Item 20)
Further Lumen Gentium, in 1964, orders the restoration of the permanent deaconate and permits admission of married men, citing the council’s decisions. It is signed by “+PERICLE FELICI, Titular Archbishop of Samosata, Secretary General of the Second Vatican Ecumenical Council”
It’s not crystal clear, but it does affirm only the eastern concept of major orders, which is also the modern concept in the Roman church… and it does not include the minor orders as part of deaconal formation.
Prior roman delineations (Pius IX, for example) list subdeacons with the deacons and priests as assistants to the bishops. Therefore, this represents a state change. The bishops I’ve seen write of it understood it to be because of a flawed Roman theologumenion of subdeacons as major orders… clearly not the belief of the early church, nor of the Catholic East, nor their Orthodox brethren.
His Holiness Paul VI, in promulgating his moto proprio, is NOT advocating on his own (he cites lumen gentium) in restoring the permanent deaconate. He merely restates Lumen Gentium and makes it clear it will happen because it is moto proprio… “to move properly.”
There are other post-conciliar documents from concila estabished by the council which are relevant, but not online; I don’t have my text copies to hand.
vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_const_19641121_lumen-gentium_en.html
vatican.va/holy_father/paul_vi/motu_proprio/documents/hf_p-vi_motu-proprio_19670618_sacrum-diaconatus_en.html