Merge branch 'net-dsa-yt921x-add-support-for-motorcomm-yt921x'

David Yang says:

====================
net: dsa: yt921x: Add support for Motorcomm YT921x

Motorcomm YT921x is a series of ethernet switches developed by Shanghai
Motorcomm Electronic Technology, including:

  - YT9215S / YT9215RB / YT9215SC: 5 GbE phys
  - YT9213NB / YT9214NB: 2 GbE phys
  - YT9218N / YT9218MB: 8 GbE phys

and up to 2 serdes interfaces.

This patch adds basic support for a working DSA switch.
====================

Link: https://patch.msgid.link/20251017060859.326450-1-mmyangfl@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>