Is it truly necessary that all these drivers run in the kernel space? I bet a lot of drivers are just interfacing with a standard serial line which could be do

Is it truly necessary that all these drivers run in the kernel space? I bet a lot of drivers are just interfacing with a standard serial line which could be done in the stable user space and then exposing the next layer through something like FUSE. If I understand treble correctly that’s close to what Android is doing, where each HAL can be done in userspace?