They're usually also in U-boot in ROM. The trees in the kernel override the platform's one because the kernel is newer and knows better. ACPI on x86 works the

They're usually also in U-boot in ROM. The trees in the kernel override the platform's one because the kernel is newer and knows better. ACPI on x86 works the same way - it's in ROM but the OS doesn't necessarily use it blindly, it has plenty of quirks to interpret it with.