dt-bindings: net: sparx5: document RGMII delays

The lan969x switch device supports two RGMII port interfaces that can be
configured for MAC level rx and tx delays. Document two new properties
{rx,tx}-internal-delay-ps in the bindings, used to select these delays.

Tested-by: Robert Marko <robert.marko@sartura.hr>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241220-sparx5-lan969x-switch-driver-4-v5-9-fa8ba5dff732@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/microchip,sparx5-switch.yaml

@@ -129,6 +129,24 @@ properties:
             minimum: 0
             maximum: 383
 
+          rx-internal-delay-ps:
+            description:
+              RGMII Receive Clock Delay defined in pico seconds, used to select
+              the DLL phase shift between 1000 ps (45 degree shift at 1Gbps) and
+              3300 ps (147 degree shift at 1Gbps). A value of 0 ps will disable
+              any delay. The Default is no delay.
+            enum: [0, 1000, 1700, 2000, 2500, 3000, 3300]
+            default: 0
+
+          tx-internal-delay-ps:
+            description:
+              RGMII Transmit Clock Delay defined in pico seconds, used to select
+              the DLL phase shift between 1000 ps (45 degree shift at 1Gbps) and
+              3300 ps (147 degree shift at 1Gbps). A value of 0 ps will disable
+              any delay. The Default is no delay.
+            enum: [0, 1000, 1700, 2000, 2500, 3000, 3300]
+            default: 0
+
         required:
           - reg
           - phys