Merge branch 'net-mdio-add-amlogic-gxl-mdio-mux-support'

Merge branch 'net-mdio-add-amlogic-gxl-mdio-mux-support'

Jerome Brunet says:

====================
net: mdio: add amlogic gxl mdio mux support

Add support for the MDIO multiplexer found in the Amlogic GXL SoC family.
This multiplexer allows to choose between the external (SoC pins) MDIO bus,
or the internal one leading to the integrated 10/100M PHY.

This multiplexer has been handled with the mdio-mux-mmioreg generic driver
so far. When it was added, it was thought the logic was handled by a
single register.

It turns out more than a single register need to be properly set.
As long as the device is using the Amlogic vendor bootloader, or upstream
u-boot with net support, it is working fine since the kernel is inheriting
the bootloader settings. Without net support in the bootloader, this glue
comes unset in the kernel and only the external path may operate properly.

With this driver (and the associated change in
arch/arm64/boot/dts/amlogic/meson-gxl.dtsi), the kernel no longer relies
on the bootloader to set things up, fixing the problem.
====================

Link: https://lore.kernel.org/r/20230130151616.375168-1-jbrunet@baylibre.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>