He'll work under P.J. Carlesimo. I'm happy for him. It's a great move by both sides. Brooks gets to work with one of the most exciting young rosters in the league; Seattle gets an assistant who should be a head coach. A win-win-win.
It's too bad how Brooks' 'return home' to Northern California turned out. All reports say he was the good soldier last year, having every opportunity to mutiny against Eric Musselman but holding out for his own off-season chance. But he might be in a better situation now anyways. Good luck to him.