All of what Brian said is true for 9front as well. If you want to see our code implementation of this you can find
it in /sys/src/9/bcm/ether4330.c. The only difference is that 9front puts firmware in /lib/firmware and not /sys/lib/firmware.
We do not provide the binary files ourselves you need to acquire them from the rasbian ISO. It should be located within
the raspbian ISO, within the fat32 partition there.