Merge branch 'net-dsa-motorcomm-add-serdes-pcs'

David Yang says:

====================
net: dsa: motorcomm: Add SerDes PCS

Rework chip_info to tell SERDES ports from xMII ones, identify the port type
at runtime from the pad configuration, and add a phylink PCS driver for the
internal SerDes, so that the link of SERDES ports can be established through
in-band negotiation instead of a fixed configuration.
====================

Link: https://patch.msgid.link/20260923021945.2203368-1-mmyangfl@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>