dt-bindings: mstar: Add binding details for mstar,smpctrl

This adds a YAML description of the smpctrl node needed by the
platform code for the MStar/SigmaStar Armv7 SoCs to boot secondary cpus.

Signed-off-by: Daniel Palmer <daniel@0x0f.com>
Link: https://lore.kernel.org/r/20201201134330.3037007-2-daniel@0x0f.com'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/arm/mstar/mstar,smpctrl.yaml

@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2020 thingy.jp.
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/arm/mstar/mstar,smpctrl.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: MStar/SigmaStar Armv7 SoC SMP control registers
+
+maintainers:
+  - Daniel Palmer <daniel@thingy.jp>
+
+description: |
+  MStar/SigmaStar's Armv7 SoCs that have more than one processor
+  have a region of registers that allow setting the boot address
+  and a magic number that allows secondary processors to leave
+  the loop they are parked in by the boot ROM.
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - sstar,ssd201-smpctrl # SSD201/SSD202D
+      - const: mstar,smpctrl
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    smpctrl@204000 {
+        compatible = "sstar,ssd201-smpctrl", "mstar,smpctrl";
+        reg = <0x204000 0x200>;
+    };