I have not seen any activity from MIPS on GCC for years.

Making a Linux port for a given MIPS based SoC is a known pain. They should've worked towards not requiring any hardcoded configuration for each SoC at all, like Linux on ARM does these days.

Do you mean the device tree?

I thought all major kernel archs were on device trees now...

Yes now, but last time I talked with people who dealt with them, people spoke of their new cores coming with "prehistoric kernels" on usb sticks.

So every vendor had to upstream their own soc in its own