Add the possibility for the RK3588 PCIe PHYs to use an internal clock instead of
a clock provided on a pin of the device. This allows boards that don't have a
PCIe clock connected to the reference pad to still function in separate clock
mode by using an internal reference clock for the PCIe PHYs.

This was tested with a CM3588 compute module on a custom PCB.

Without the new option, the default behaviour (PHYs using external pad for clock)
is applied, to keep compatibility with existing device trees.

Differences from V1 [1] :

- Documented the phy-ref-use-pad option in the DT bindings.
- Documented the extra optional differential clocks for the PHYs in the DT
  bindings.

[1] https://lore.kernel.org/all/20250715105820.4037272-1-rick.wertenbroek@gmail.com/

Rick Wertenbroek (3):
  dt-bindings: phy: rockchip,pcie3-phy: add optional differential phy
    clocks
  phy: rockchip-snps-pcie3: add support for rockchip,phy-ref-use-pad
  dt-bindings: phy: rockchip,pcie3-phy: add rockchip,phy-ref-use-pad

 .../bindings/phy/rockchip,pcie3-phy.yaml      | 21 ++++++++++--
 .../phy/rockchip/phy-rockchip-snps-pcie3.c    | 32 +++++++++++++++++++
 2 files changed, 50 insertions(+), 3 deletions(-)

-- 
2.25.1