dt-bindings: clock: airoha: Add PHY binding for Serdes port

Add PHY cell property for Serdes port selection. Currently supported only
for Airoha AN7581 SoC, that support up to 4 Serdes port.

The Serdes port can support both PCIe, USB3 or Ethernet mode.

- PCIe1 Serdes can support PCIe or Ethernet mode.
- PCIe2 Serdes can support PCIe or Ethernet mode.
- USB1 Serdes can support USB3 or HSGMII mode.
- USB2 Serdes can support USB3 or PCIe mode.

Add bindings to permit correct reference of the Serdes ports in DT.
Values are just symbolic and enumerates the Serdes port with a specific
number for precise reference.

The available Serdes port can be selected following the dt-binding header
in [2].

[2] <include/dt-bindings/soc/airoha,scu-ssr.h>

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Brian Masney <bmasney@redhat.com>

Documentation/devicetree/bindings/clock/airoha,en7523-scu.yaml

@@ -23,6 +23,7 @@ description: |
 
   All these identifiers can be found in:
   [1]: <include/dt-bindings/clock/en7523-clk.h>.
+  [2]: <include/dt-bindings/soc/airoha,scu-ssr.h>.
 
   The clocks are provided inside a system controller node.
 
@@ -50,6 +51,12 @@ properties:
     description: ID of the controller reset line
     const: 1
 
+  '#phy-cells':
+    description:
+      The first cell indicates the serdes phy number, see [2] for the
+      available serdes port.
+    const: 1
+
 required:
   - compatible
   - reg
@@ -65,12 +72,23 @@ allOf:
         reg:
           minItems: 2
 
+        '#phy-cells': false
+
   - if:
       properties:
         compatible:
-          enum:
-            - airoha,en7581-scu
-            - econet,en751221-scu
+          const: econet,en751221-scu
+    then:
+      properties:
+        reg:
+          maxItems: 1
+
+        '#phy-cells': false
+
+  - if:
+      properties:
+        compatible:
+          const: airoha,en7581-scu
     then:
       properties:
         reg:

include/dt-bindings/soc/airoha,scu-ssr.h

@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
+
+#ifndef __DT_BINDINGS_AIROHA_SCU_SSR_H
+#define __DT_BINDINGS_AIROHA_SCU_SSR_H
+
+#define AIROHA_SCU_SERDES_PCIE1		0
+#define AIROHA_SCU_SERDES_PCIE2		1
+#define AIROHA_SCU_SERDES_USB1		2
+#define AIROHA_SCU_SERDES_USB2		3
+
+#endif /* __DT_BINDINGS_AIROHA_SCU_SSR_H */