cpu: Rename CPU_ARCH to CPU_CORE

[leandrolanzieri]

Contribution description

Currently cortexm and mips CPUs are using the variable CPU_ARCH to refer to the CPU core identifier. Even the documentation of this variable indicates that:

RIOT/makefiles/vars.inc.mk

Line 15 in 58cd126

export CPU_ARCH # The specific identifier of the core present in the CPU, used currently only for ARM CPU's. Needed for depency resolution.

A naming discussion started in #14176 regarding our classification system for our CPUs. It makes sense to structure the names using the correct terms. This PR introduces CPU_CORE as a replacement for CPU_ARCH, and assigns the correct architecture value to cortexm and mips CPUs.

Testing procedure

• Use make dependency-debug to check that the correct CPU_CORE and CPU_ARCH is assign to the boards

Issues/PRs references

Somehow related to #14176

[MrKevinWeiss]

Tested with for board in $(make info-boards --no-print-directory); do printf "%s=" ${board}; BOARD=${board} make --no-print-directory info-debug-variable-CPU_CORE -C examples/hello-world/; done
and for board in $(make info-boards --no-print-directory); do printf "%s=" ${board}; BOARD=${board} make --no-print-directory info-debug-variable-CPU_ARCH -C examples/hello-world/; done.

Assuming murdock passes I think this would be OK. I will ACK! @kaspar030 has your comment been addressed and @fjmolinas any last words?

[fjmolinas]

I haven't taken a detailed look, but +1 for the general idea.

[kaspar030]

This PR introduces CPU_CORE as a replacement for CPU_ARCH, and assigns the correct architecture value to cortexm and mips CPUs.

Could you sum up the state we have and will have? I'm honestly confused.

[leandrolanzieri]

Could you sum up the state we have and will have? I'm honestly confused.

Currently CPU_ARCH variable is being used only in cortexm and mips CPUs to indicate the core of the CPU (instead of the architecture as the name suggests).

The PR moves these values to (the newly introduced variable) CPU_CORE, to use the proper terminology. CPU_ARCH is kept for the CPUs that already define it, but the correct architecture identifier is assigned to it.

For instance, a CPU that currently has CPU_ARCH=cortex-m0plus, with this PR will have CPU_CORE=cortex-m0plus and CPU_ARCH=armv6m.

[MrKevinWeiss]

@kaspar030 It makes sense to me, is there anything else that you can think of that this clarification of naming might effect (ie. anything with murdock or if something is used outside RIOT)?

[fjmolinas]

@leandrolanzieri this one needs a rebase, other than that can you uncrustify core/include/panic.h?

[fjmolinas]

You can squash afterwards as well @leandrolanzieri!

comment addressed

[fjmolinas]

Added the testing lable, since @MrKevinWeiss tested!

[aabadie]

This needs a rebase now.

[fjmolinas]

2nd ACK