For an Agile Squad to best function, they need to be able to define what they are authoritative for, the dependencies of that squad, and describe the goals of that squad. This helps Squads define areas of autonomy, and declare clear dependencies between Squads.
Organizing people so they can achieve more than the sum of their parts is really hard. I've spent a good portion of my life working on this problem, so here are some thoughts on the matter.