dt-bindings: phy: exynos: add the samsung,exynos-pcie-phy binding

Add dt-bindings for the Samsung Exynos PCIe PHY controller (Exynos5433
variant). Based on the text dt-binding posted by Jaehoon Chung.

Link: https://lore.kernel.org/r/20201113170139.29956-4-m.szyprowski@samsung.comSigned-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/phy/samsung,exynos-pcie-phy.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/phy/samsung,exynos-pcie-phy.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Samsung SoC series PCIe PHY Device Tree Bindings
+
+maintainers:
+  - Marek Szyprowski <m.szyprowski@samsung.com>
+  - Jaehoon Chung <jh80.chung@samsung.com>
+
+properties:
+  "#phy-cells":
+    const: 0
+
+  compatible:
+    const: samsung,exynos5433-pcie-phy
+
+  reg:
+    maxItems: 1
+
+  samsung,pmu-syscon:
+    $ref: '/schemas/types.yaml#/definitions/phandle'
+    description: phandle for PMU system controller interface, used to
+                 control PMU registers bits for PCIe PHY
+
+  samsung,fsys-sysreg:
+    $ref: '/schemas/types.yaml#/definitions/phandle'
+    description: phandle for FSYS sysreg interface, used to control
+                 sysreg registers bits for PCIe PHY
+
+required:
+  - "#phy-cells"
+  - compatible
+  - reg
+  - samsung,pmu-syscon
+  - samsung,fsys-sysreg
+
+additionalProperties: false
+
+examples:
+  - |
+    pcie_phy: pcie-phy@15680000 {
+        compatible = "samsung,exynos5433-pcie-phy";
+        reg = <0x15680000 0x1000>;
+        samsung,pmu-syscon = <&pmu_system_controller>;
+        samsung,fsys-sysreg = <&syscon_fsys>;
+        #phy-cells = <0>;
+    };
+...