https://docs.tinygrad.org/tinygpu/ are their docs, and https://github.com/tinygrad/tinygrad/tree/4d36366717aa9f1735... is the actual (user space) driver.

My read of everything is that they are using Docker for NVIDIA GPUs for the sake of "how do you compile code to target the GPU"; for AMD they're just compiling their own LLVM with the appropriate target on macOS.