My opinion is the Sean McDermott is from a branch of the Jim Johnson tree. Ron Rivera, Leslie Frazier, and Sean McDermott all are in a group of people that think in a similar fashion.
I suppose you can also say technically McDermott is from the Andy Reid tree. But offensive and defensive coaches think differently so I don't see this as helpful except for the cheating tree of Belichick. But keep in mind BB is no longer a defensive coach. He has a hand in everything.
I see Sean, Leslie, and Ron as assistants of Jim Johnson. Andy Reid is known as a high end strategic thinking coach, a master of WCO, and QB guru. Andy Reid values QB play. I am sure Sean learned things but I don't see him close to an Andy Reid at all. Brad Childress also didn't want to be his offensive coordinator which I thought was also telling.