"I was watching in the night visions, And behold, One like the Son of Man, Coming with the clouds of heaven! He came to the Ancient of Days, And they brought Him near before Him. Then to Him was given dominion and glory and a kingdom, That all peoples, nations, and languages should serve Him. His dominion is an everlasting dominion, Which shall not pass away, And His kingdom the one Which shall not be destroyed." Daniel 7:13, 14 NKJV
This is without doubt a magnificent vision of Christ, His glory and rule.
However, it is good to understand that Daniel as a Jew would have had some understanding of the concept of a Son of Man. He knew of a Messiah to come and may have very well known Him to be God's son.
His vision then of the glorious rule and dominion of God's son came in this context....