Merge branch 'enable-sgmii-and-2500basex-interface-mode-switching-for-intel-platforms'

Merge branch 'enable-sgmii-and-2500basex-interface-mode-switching-for-intel-platforms'

Choong Yong Liang says:

====================
Enable SGMII and 2500BASEX interface mode switching for Intel platforms

During the interface mode change, the 'phylink_major_config' function will
be triggered in phylink. The modification of the following functions will
support the switching between SGMII and 2500BASE-X interface modes for
the Intel platform:

- xpcs_switch_interface_mode: Re-initiates clause 37 auto-negotiation for
  the SGMII interface mode to perform auto-negotiation.
- mac_finish: Configures the SerDes according to the interface mode.

With the above changes, the code will work as follows during the interface
mode change. The PCS will reconfigure according to the pcs_neg_mode and the
selected interface mode. Then, the MAC driver will perform SerDes
configuration in 'mac_finish' based on the selected interface mode. During
the SerDes configuration, the selected interface mode will identify TSN
lane registers from FIA and then send IPC commands to the Power Management
Controller (PMC) through the PMC driver/API. The PMC will act as a proxy to
program the PLL registers.
====================

Link: https://patch.msgid.link/20250227121522.1802832-1-yong.liang.choong@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>