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.

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https://bugs.launchpad.net/bugs/1765628

Title:
  Create an image for all raspberry models

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