Comment 6 for bug 1765628

The current thinking seems to be that efi passes grub2 the flattened device tree. The problem with this is that the dtb is not at all stable. It is supposed to be independent of operating system, but there are differences between the upstream and rpi foundation kernels. Grub2 or U-boot can give the user the choice of kernel or even operating system, but it could be fed an incompatible dtb by efi. Grub2 can load a device tree which solves this, but you currently loose the overlays.

Having said all of that, the dtb is stable enough not to require always updating on every kernel update. This is how flash-kernel can get away with not updating the overlays. But the safest thing is not to update the dtb, so that the overlays are in-sync. Kernel drivers are supposed to (if they are written correctly) be able to cope with an old dtb file.

I suggest that Linux-firmware-raspi2 handles updating the dtb files, and it does so infrequently and only when necessary.