No, the coronation of Mary is not a doctrine or dogma, but a pious belief/small “t” tradition held for centuries by the faithful. Of course, it could be raised to a doctrine, but so far the Church hasn’t seen the need to do that.
To Ambrose, Seven Sorrows and Della,
Yes, the Coronation of Mary is an infallible Catholic Doctrine.
The word doctrine simply means teaching. When we capitalize it, we say that it is an infallible Teaching. And yes, the Coronation of Mary is an infallible Doctrine.
The proof that it is an infallible Doctrine can be found in Revelations 12:1, where Mary is described as being crowned with 12 stars, in heaven.
Then, we see that the same Document that declared the Assumption of Mary, declares her to be the Queen of Heaven:
*26. Often there are theologians and preachers who, following in the footsteps of the holy Fathers,(20) have been rather free in their use of events and expressions taken from Sacred Scripture to explain their belief in the Assumption. Thus, to mention only a few of the texts rather frequently cited in this fashion, some have employed the words of the psalmist: “Arise, O Lord, into your resting place: you and the ark, which you have sanctified”(21); and have looked upon the Ark of the Covenant, built of incorruptible wood and placed in the Lord’s temple, as a type of the most pure body of the Virgin Mary, preserved and exempt from all the corruption of the tomb and raised up to such glory in heaven. Treating of this subject, they also describe her as the Queen entering triumphantly into the royal halls of heaven and sitting at the right hand of the divine Redeemer.(22) Likewise they mention the Spouse of the Canticles “that goes up by the desert, as a pillar of smoke of aromatical spices, of myrrh and frankincense” to be crowned.(23) These are proposed as depicting that heavenly Queen and heavenly Spouse who has been lifted up to the courts of heaven with the divine Bridegroom.
*
w2.vatican.va/content/pius-xii/en/apost_constitutions/documents/hf_p-xii_apc_19501101_munificentissimus-deus.html
Another proof, is that it is taught in the Catechism that she is the Queen of all things:
*966 "Finally the Immaculate Virgin, preserved free from all stain of original sin, when the course of her earthly life was finished, was taken up body and soul into heavenly glory, and exalted by the Lord as
Queen over all things, so that she might be the more fully conformed to her Son, the Lord of lords and conqueror of sin and death."508 The Assumption of the Blessed Virgin is a singular participation in her Son’s Resurrection and an anticipation of the resurrection of other Christians:
In giving birth you kept your virginity; in your Dormition you did not leave the world, O Mother of God, but were joined to the source of Life. You conceived the living God and, by your prayers, will deliver our souls from death.509*
All Catholic Doctrines are infallible. Even before they are declared so by a formal Dogmatic proclamation. Thus, the Assumption was infallible Doctrine before it was declared thus by a Dogmatic proclamation. The proclamations merely confirm and define that which has previously been held as Doctrine.
I suppose you consider me a heretic as well. 
