dt-bindings: mfd: sprd: Add bindings for ums512 global registers

Add bindings for Unisoc system global register which provide register map
for clocks.
Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
Signed-off-by: Cixi Geng <cixi.geng1@unisoc.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220909152421.278662-2-gengcixi@gmail.com

Documentation/devicetree/bindings/mfd/sprd,ums512-glbreg.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2022 Unisoc Inc.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/sprd,ums512-glbreg.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Unisoc System Global Register
+
+maintainers:
+  - Orson Zhai <orsonzhai@gmail.com>
+  - Baolin Wang <baolin.wang7@gmail.com>
+  - Chunyan Zhang <zhang.lyra@gmail.com>
+
+description:
+  Unisoc system global registers provide register map
+  for clocks and some multimedia modules of the SoC.
+
+properties:
+  compatible:
+    items:
+      - const: sprd,ums512-glbregs
+      - const: syscon
+      - const: simple-mfd
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 1
+
+  ranges:
+    maxItems: 1
+
+  reg:
+    maxItems: 1
+
+patternProperties:
+  "^clock-controller@[0-9a-f]+$":
+    type: object
+    $ref: /schemas/clock/sprd,ums512-clk.yaml#
+    description:
+      Clock controller for the SoC clocks.
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    ap_apb_regs: syscon@71000000 {
+      compatible = "sprd,ums512-glbregs", "syscon", "simple-mfd";
+      reg = <0x71000000 0x3000>;
+      #address-cells = <1>;
+      #size-cells = <1>;
+      ranges = <0 0x71000000 0x3000>;
+
+      clock-controller@0 {
+        compatible = "sprd,ums512-apahb-gate";
+        reg = <0x0 0x2000>;
+        #clock-cells = <1>;
+      };
+    };
+
+  - |
+    ap_intc5_regs: syscon@32360000 {
+      compatible = "sprd,ums512-glbregs", "syscon", "simple-mfd";
+      reg = <0x32360000 0x1000>;
+    };