It's nothing to do with that really. It's much more to do with the gen10 (Gxxx) Mali requiring a completely new kernel driver. Given that nouveau and other drivers required the same thing, this ended up being a long diversion into a lot of new common DRM infrastructure to make things easier for the next drivers who need to do the same thing. By comparison, enabling gen9 in the kernel was more like adding a couple of device IDs. See bbrezillon & dakr's talk here for more details: https://indico.freedesktop.org/event/4/contributions/181/