dt-bindings: bus: Add MIPS CDMM controller

It's a Common Device Memory Map controller embedded into the MIPS IP
cores, which dts node is supposed to have compatible and reg properties.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Documentation/devicetree/bindings/bus/mti,mips-cdmm.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/bus/mti,mips-cdmm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: MIPS Common Device Memory Map
+
+description: |
+  Defines a location of the MIPS Common Device Memory Map registers.
+
+maintainers:
+  - James Hogan <jhogan@kernel.org>
+
+properties:
+  compatible:
+    const: mti,mips-cdmm
+
+  reg:
+    description: |
+      Base address and size of an unoccupied memory region, which will be
+      used to map the MIPS CDMM registers block.
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+examples:
+  - |
+    cdmm@1bde8000 {
+      compatible = "mti,mips-cdmm";
+      reg = <0x1bde8000 0x8000>;
+    };
+...