dt-bindings: Add AXG PCIE PHY bindings

Add documentation for PCIE PHYs found in AXG SoCs.
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/phy/amlogic,meson-axg-pcie.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/phy/amlogic,meson-axg-pcie.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Amlogic AXG PCIE PHY
+
+maintainers:
+  - Remi Pommarel <repk@triplefau.lt>
+
+properties:
+  compatible:
+    const: amlogic,axg-pcie-phy
+
+  reg:
+    maxItems: 1
+
+  resets:
+    maxItems: 1
+
+  phys:
+    maxItems: 1
+
+  phy-names:
+    const: analog
+
+  "#phy-cells":
+    const: 0
+
+required:
+  - compatible
+  - reg
+  - phys
+  - phy-names
+  - resets
+  - "#phy-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/reset/amlogic,meson-axg-reset.h>
+    #include <dt-bindings/phy/phy.h>
+    pcie_phy: pcie-phy@ff644000 {
+          compatible = "amlogic,axg-pcie-phy";
+          reg = <0x0 0xff644000 0x0 0x1c>;
+          resets = <&reset RESET_PCIE_PHY>;
+          phys = <&mipi_analog_phy PHY_TYPE_PCIE>;
+          phy-names = "analog";
+          #phy-cells = <0>;
+    };