The grammar and puncution idenfities the Father as the one Lord because He is over all. The Father is that one Spirit, Lord, and God over Jesus and everyone else. This is a doctrine as well. Paul went around the Roman empure teaching others that Jesus belongs to God, that God is the head of Jesus, that Jesus will be made subject to God, Jesus is a man with a God, a man who serves God, etc.
Eph. 4
4There is one body and one Spirit, just as you were called to one hope when you were called;
5one Lord, one faith, one baptism;
6one God and Father of all, who is over all and through all and in all.