Fixes: #72374
Support extending an existing SoC with new CPU clusters.
This commit introduces the following changes to allow an SoC to be
extended out-of-tree.
The SoC yaml schema is extended to support an extend field which
will be used to identify the SoC to be extended with extra CPU clusters.
A SoC 'a_soc' can be extended like this:
> socs:
> extend: a_soc
> cpuclusters:
> - name: extra_core
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
98b186c110