[PATCH net-next v10 0/6] net: pcs: add basic support for RK3568 XPCS

This series adds proper SGMII support for the Rockchip RK3568 SoC
using the integrated Synopsys DesignWare XPCS, along with necessary
fixes and refactoring in the stmmac core and XPCS driver.

Motivation
==========
The RK3568 integrates a DW XPCS accessed via APB3 and connected to
a Naneng Combo SerDes PHY.  Several boards (e.g., Ariaboard
Photonicat) use this interface for Gigabit Ethernet.  However, the
current upstream stmmac driver does not support this configuration,
and the XPCS driver has issues in SGMII poll mode that cause the
link to be reported incorrectly.

This series addresses these issues by:
- Adding ANRESTART support for SGMII link recovery
- Adding a Rockchip XPCS platform glue driver and wiring it up in
  dwmac-rk

Series overview
===============

RK3568 XPCS/SGMII:
  Patch 1: DT binding for Rockchip RK3568 XPCS
  Patch 2: add ANRESTART support for SGMII link recovery
  Patch 3: implement the Rockchip XPCS platform glue driver
  Patch 4: DT binding for Rockchip DWMAC PCS
  Patch 5: wire up SGMII support in dwmac-rk
  Patch 6: update MAINTAINERS

Dependencies
============
- Generic PM domain (genpd) changes:
  https://lore.kernel.org/all/20260925041751.495818-1-coiaprant@gmail.com/ (local)
- PHY binding+driver (Naneng Combo PHY SGMII MAC selection):
  https://lore.kernel.org/all/20261005221229.1095843-1-coiaprant@gmail.com/ (local)
- stmmac XPCS lifetime management fix:
  https://lore.kernel.org/all/20261005221749.1104430-1-coiaprant@gmail.com/ (local)

The DTS changes using the PHY property are sent separately to
Heiko/linux-rockchip. There is no hard build dependency; the pieces
can converge during the merge window.

Changelog
=========

- Resend and split: PHY binding+driver sent to linux-phy, stmmac
  lifetime fix and XPCS binding sent separately, DTS sent to
  linux-rockchip.

Key design decisions
====================
- The stmmac core now delegates XPCS creation entirely to platform
  drivers via pcs_init/pcs_exit.  This is necessary because the
  generic XPCS creation logic would override any XPCS set up by the
  platform driver.

- The Rockchip XPCS driver creates a virtual MDIO bus over the APB3
  registers and implements address remapping.  The generic XPCS core
  handles all PCS configuration via phylink_pcs_ops.

- On RK3568 in SGMII mode, the MAC clock is fixed at 125 MHz and
  cannot be dynamically changed.  In-band mode is used, and the
  generic stmmac set_clk_tx_rate callback is disabled to prevent
  incorrect clock updates that would break RX.

- The SerDes and power domain are attached to the XPCS device tree
  node rather than the MAC node. This reflects the actual hardware
  topology and simplifies the dwmac-rk driver by keeping all PCS-related
  resources self-contained. It also prepares for possible future QSGMII
  support, where a single SerDes serves multiple MACs and would be
  more naturally managed under the XPCS node.

Testing
=======
Board: Ariaboard Photonicat (RK3568)
OS: Armbian (trixie)
Kernel: 6.18 (backports)
Result: The SGMII interface obtains an IP address, SSH works, and
        ping traffic passes without loss.

Notes
=====
- When testing out-band mode with set_clk_tx_rate, only 1000Mbps
  works on both TX/RX; 10/100Mbps only works on TX side.

Acknowledgments
===============
This work was inspired by and builds upon the excellent work of others:
- Serge Semin's Synopsys DesignWare XPCS platform driver (pcs-xpcs-plat.c)
- Clément Léger's Renesas MIIC driver (pcs-rzn1-miic.c)
- The Rockchip TRM and downstream OEM drivers

Thanks in advance,
Coia Prant
---
Coia Prant (6):
  dt-bindings: net: pcs: add rockchip,rk3568-xpcs support
  net: pcs: xpcs: add ANRESTART support for SGMII link recovery
  net: pcs: xpcs: add Rockchip RK3568 platform glue driver
  dt-bindings: net: rockchip-dwmac: document pcs-handle
  net: stmmac: dwmac-rk: add SGMII support for RK3568
  MAINTAINERS: add entry for Rockchip XPCS driver

 .../net/pcs/rockchip,rk3568-xpcs.yaml         | 110 ++++
 .../bindings/net/rockchip-dwmac.yaml          |  18 +
 MAINTAINERS                                   |   9 +
 drivers/net/ethernet/stmicro/stmmac/Kconfig   |   1 +
 .../net/ethernet/stmicro/stmmac/dwmac-rk.c    | 130 +++-
 drivers/net/pcs/Kconfig                       |  25 +
 drivers/net/pcs/Makefile                      |   5 +-
 drivers/net/pcs/pcs-xpcs-rk.c                 | 619 ++++++++++++++++++
 drivers/net/pcs/pcs-xpcs.c                    |  35 +-
 include/linux/pcs/pcs-xpcs-rk.h               |  11 +
 10 files changed, 935 insertions(+), 28 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/net/pcs/rockchip,rk3568-xpcs.yaml
 create mode 100644 drivers/net/pcs/pcs-xpcs-rk.c
 create mode 100644 include/linux/pcs/pcs-xpcs-rk.h

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