This make the process of applying overlays more reliable by:
1. Ignoring dtb files that are not really device trees. [^1]
2. Adding a `filter` option (per-overlay, there already is a global one)
to limit the files to which the overlay applies. This is useful
in cases where the `compatible` string is ambiguous and multiple
unrelated files match.
Previously the script would fail in both cases.
[^1]: For example, there is dtbs/overlays/overlay_map.dtb in the
Raspberry Pi 1 kernel.
Now allows applying external overlays either in form of
.dts file, literal dts context added to store or precompiled .dtbo.
If overlays are defined, kernel device-trees are compiled with '-@'
so the .dtb files contain symbols which we can reference in our
overlays.
Since `fdtoverlay` doesn't respect `/ compatible` by itself
we query compatible strings of both `dtb` and `dtbo(verlay)`
and apply only if latter is substring of the former.
Also adds support for filtering .dtb files (as there are now nearly 1k
dtbs).
Co-authored-by: georgewhewell <georgerw@gmail.com>
Co-authored-by: Kai Wohlfahrt <kai.wohlfahrt@gmail.com>
