MAINTAINERS: add a limited ARM and ARM64 SoC entry

It is expected for ARM and ARM64 SoC related code to go through
sub-architecture maintainers.  Their addresses were therefore not
documented to push patch traffic through sub-architecture maintainers.

However when patches touch generic code, e.g. multi_v7_defconfig, the
patch might not be picked up by them and instead should go to the SoC
maintainers - Arnd and Olof.

Add a minimal maintainer's entry for SoC covering only Makefile, so it
will not appear on most of submissions (except new devicetree boards).
It will though serve as a documentation and reference for cases when
submitter does not know where to send his SoC-related patches.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201201211516.24921-2-krzk@kernel.org'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

@@ -1486,6 +1486,16 @@ F:	Documentation/devicetree/bindings/iommu/arm,smmu*
 F:	drivers/iommu/arm/
 F:	drivers/iommu/io-pgtable-arm*
 
+ARM AND ARM64 SoC SUB-ARCHITECTURES (COMMON PARTS)
+M:	Arnd Bergmann <arnd@arndb.de>
+M:	Olof Johansson <olof@lixom.net>
+M:	soc@kernel.org
+L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
+S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git
+F:	arch/arm/boot/dts/Makefile
+F:	arch/arm64/boot/dts/Makefile
+
 ARM SUB-ARCHITECTURES
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained