bga layout
When doing BGA fanout there are a lot of things to consider like the BGA pitch, the ball dimensions, the via's that can be used, nr of layers, position op power pins, placement of decoupling capacitors etc.
whenever possible use courtyard via's to connect to the other layers and continue the connections. try to group signals together like busses and seperate high speed signals from the rest.
Doing a g**gle search on 'BGA fanout patterns" will also find a lot of information