dt-bindings: PCI: dwc: Add phys/phy-names common properties

It's normal to have the DW PCIe RP/EP DT-nodes equipped with the explicit
PHY phandle references. There can be up to 16 PHYs attach in accordance
with the maximum number of supported PCIe lanes. Let's extend the common
DW PCIe controller schema with the 'phys' and 'phy-names' properties
definition. There two types PHY names are defined: preferred generic names
'^pcie[0-9]+$' and non-preferred vendor-specific names
'^pcie([0-9]+|-?phy[0-9]*)?$' so to match the names currently supported by
the DW PCIe platform drivers ("pcie": meson; "pciephy": qcom, imx6;
"pcie-phy": uniphier, rockchip, spear13xx; "pcie": intel-gw; "pcie-phy%d":
keystone, dra7xx; "pcie": histb, etc).

Link: https://lore.kernel.org/r/20221113191301.5526-6-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml

@@ -17,6 +17,30 @@ description:
 select: false
 
 properties:
+  phys:
+    description:
+      There can be up to the number of possible lanes PHYs specified placed in
+      the phandle array in the line-based order. Obviously each the specified
+      PHYs are supposed to be able to work in the PCIe mode with a speed
+      implied by the DWC PCIe controller they are attached to.
+    minItems: 1
+    maxItems: 16
+
+  phy-names:
+    minItems: 1
+    maxItems: 16
+    oneOf:
+      - description: Generic PHY names
+        items:
+          pattern: '^pcie[0-9]+$'
+      - description:
+          Vendor-specific PHY names. Consider using the generic
+          names above for new bindings.
+        items:
+          oneOf:
+            - pattern: '^pcie(-?phy[0-9]*)?$'
+            - pattern: '^p2u-[0-7]$'
+
   reset-gpio:
     deprecated: true
     description:

Documentation/devicetree/bindings/pci/snps,dw-pcie-ep.yaml

@@ -52,4 +52,7 @@ examples:
             <0xdfc01000 0x0001000>, /* IP registers 2 */
             <0xd0000000 0x2000000>; /* Configuration space */
       reg-names = "dbi", "dbi2", "addr_space";
+
+      phys = <&pcie_phy0>, <&pcie_phy1>, <&pcie_phy2>, <&pcie_phy3>;
+      phy-names = "pcie0", "pcie1", "pcie2", "pcie3";
     };

Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml

@@ -70,5 +70,8 @@ examples:
 
       reset-gpios = <&port0 0 1>;
 
+      phys = <&pcie_phy>;
+      phy-names = "pcie";
+
       num-lanes = <1>;
     };