Jesus said that God the Father is Spirit, but the Holy Spirit has limitations imposed upon Him (if I'm understanding Christ). Jesus said that He, the Holy Spirit, is One like Him, but takes of what is His (Christ's) and gives it to us and that all that is the Father’s is His. I think that this covers the trinity pretty clearly. In that relationship, the Holy Spirit is subordinate to the Lord, yet Jesus is called the Son of God because he was begotten of the Holy Spirit. This order of subordination of Spirit to Son to Father is functional in each having their own role or purpose (if you can say that of God), but Jesus acknowledged that the Father is greater than Him if for no other reason than Jesus taking on the limitations of the "Son of Man" and suffering temptation. It is impossible that the Father suffer temptation as He can do whatever He wills.
I believe that the Holy Spirit is the Father, but with the imposed limitation of interacting with us in time. Time is part of creation, but the Father exists apart from creation in eternity. How can He who exists outside of His creation, interact with that creation except by taking on the limitations of creation and entering it in the person of His Son and His Holy Spirit?
The Trinity is not nearly as complicated as people imagine when you understand that time is part of creation and this truth is revealed in the very first chapter of genesis, when the Lord created the first day. How could there be time without the first night and the first day? I would think that the Revelation of God would be utterly impossible if there were no Trinity (if you hold scripture to be true.)
The problem is that the carnal mind remains "veiled" to scripture until the Holy Spirit lifts the veil and allows us to see His Christ.