The meaning of the concept of Son of Man:
Jesus referring to himself makes the following statement: "I am the door, by me if any man enter will be saved" Luke 10:9.
Door means entrance and in this case entrance to the knowledge of God, to the knowledge of the wisdom, of the Word.
Christ tells us that he personifies the wisdom of God, the access to the science of God, remember that the wisdom is the science of the ultimate causes according to Aristotle, the knowledge of the correct means to live and also called the key of science in Luke 11:52. Wisdom is the first and perfect science.
Wisdom is the science of the being and the truth and therefore through it, we access to all knowledge, the wisdom is the door or access to all human knowledge.The Wisdom is a perfection of God, a gift, God is wise, God is the wisdom itself.
The spiritual gifts are perfections.The mysteries of the Kingdom of God in essence are the mysteries of eternal life and wisdom, the charisms are infused.
Kingdom of God means empire, kingdom, dominion of the divine perfections. "Be perfect, therefore, as your heavenly father is perfect" Matthew 5:48.
The Kingdom of God is not the church, it is the doctrine of those who are "full of the spirit", of the wise as God is wise.
In more general terms, the Gospels explain that Christ personifies the charisms of God.
So we can say that the kingdom of God has a double meaning, the man makes himself "son of God" that is to say the man lives the gifts of God. And on the other side God "became son of man" or to say the perfections of God are personified in Christ.