Comment 0 for bug 1850678

Specific to the Raspberry Pi, when flash-kernel is executed to copy things to the boot partition, only the dtb of the Pi that it is being executed on is copied. In order to support moving the SD card between Pi models, flash-kernel needs to copy *all* dtbs provided by the kernel to the boot partition.

Consider the case of SRUing Pi 4 support to Bionic. Bionic does not currently support the Pi 4, so a user must necessarily boot their Bionic image on, say, a Pi 3. If they then upgrade to a kernel supporting the Pi 4, flash-kernel will only copy the dtb for the Pi 3 to the boot partition. If the card is then moved to a Pi 4 it will fail to boot due to a missing device-tree.