Commit a21bf90e ("brcmfmac: use ISO3166 country code and 0 rev as
fallback on some devices") introduced a fallback mechanism whereby a
trivial mapping from ISO3166 country codes to firmware country code and
revision is used on some devices. This fallback operates on the device
level, so it is enabled only for certain supported chipsets.

In general though, the firmware country codes are determined by the CLM
blob, which is board-specific and may vary despite the underlying
chipset being the same.

The aforementioned commit is actually a refinement of a previous commit
that was reverted in commit 151a7c12 ("Revert "brcmfmac: use ISO3166
country code and 0 rev as fallback"") due to regressions with a BCM4359
device. The refinement restricted the fallback mechanism to specific
chipsets such as the BCM4345.

We use a chipset - CYW88359 - that the driver identifies as a BCM4359
too. But in our case, the CLM blob uses ISO3166 country codes
internally, and all with revision 0. So the trivial mapping is exactly
what is needed in order for the driver to sync the kernel regulatory
domain to the firmware. This is just a matter of how the CLM blob was
prepared by the hardware vendor. The same could hold for other boards
too.

Although the brcm,ccode-map device tree property is useful for cases
where the mapping is more complex, the trivial case invites a much
simpler specification. This patch adds support for parsing the
brcm,ccode-map-trivial device tree property. Subordinate to the more
specific brcm,ccode-map property, this new proprety simply informs the
driver that the fallback method should be used in every case.

In the absence of the new property in the device tree, expect no
functional change.
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220711123005.3055300-3-alvin@pqrs.dk