If you're using gitflow, you've got a separate develop branch that everybody merges to, while master remains stable. Only when develop works and passes its tests, can it be merged to master.

And with multiple teams sharing the same code base, breaking master is going to slow a lot of people down a lot more.

I have little experience with multiple teams working on a single code base, but it sounds like a recipe for disaster no matter how you organise that. Make your code as modular as possible, so each team can take responsibility for their own code.