Merge branch 'add-starfive-jhb100-soc-sgmii-gmac-support'

Minda Chen says:

====================
Add StarFive jhb100 soc SGMII GMAC support

jhb100 is a Starfive new RISC-V SoC for datacenter BMC (BaseBoard
Managent Controller). Similar with Aspeed 27x0.

The jhb100 minimal system upstream is in progress:
https://patchwork.kernel.org/project/linux-riscv/cover/20260508053632.818548-1-changhuang.liang@starfivetech.com/

jhb100 GMAC still using designware GMAC core like JH7100 and JH7110,
and contains 2 SGMII interfaces, 1 RGMII/RMII interface, 1 RMII
interface. In JH7100/JH7110 dwmac-starfive.c have supported RGMII/RMII
interface. So require to add SGMII support to dwmac-starfive.c for JHB100.

SGMII serdes PHY has been integrated in JHB100 and do not have driver
setting.

In JHB100 EVB board, SGMII connect with motorcomm YT8531s external PHY
and support RJ45 ethernet port.
====================

Link: https://patch.msgid.link/20260527084108.121416-1-minda.chen@starfivetech.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>