alt Hacker NewsIts the kernel drivers, not firmware. There is no bios or acpi, so the kernel itself has to support a specifc board. In practice it means there is a dtb file that configures it and the actual drivers in the kernel.
Manufacturers hack it together, flash to device and publish the sources, but dont bother with upstreaming and move on.
Same story as android devices not having updates two years after release.
But "no BOIS or ACPI" and requiring the kernel to support each individual board sounds exactly like the problem is the ARM architecture in general. Until that's sorted it makes sense to be wary of ARM.