Add a PCS driver for the MII converter that is present on the Renesas
RZ/N1 SoC. This MII converter is reponsible for converting MII to
RMII/RGMII or act as a MII pass-trough. Exposing it as a PCS allows to
reuse it in both the switch driver and the stmmac driver. Currently,
this driver only allows the PCS to be used by the dual Cortex-A7
subsystem since the register locking system is not used.
Signed-off-by: Clément Léger <clement.leger@xxxxxxxxxxx>
Reviewed-by: Vladimir Oltean <olteanv@xxxxxxxxx>