dt-bindings: hwlock: add sun6i_hwspinlock

Adds documentation on how to use the sun6i_hwspinlock driver for sun6i
compatible series SoCs.
Reviewed-by: Samuel Holland <samuel@sholland.org>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net>
Link: https://lore.kernel.org/r/b7a1f5532e0ae474473858055fd9bbabff9e1449.1615713499.git.wilken.gottwalt@posteo.netSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Documentation/devicetree/bindings/hwlock/allwinner,sun6i-a31-hwspinlock.yaml

+# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwlock/allwinner,sun6i-hwspinlock.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SUN6I hardware spinlock driver for Allwinner sun6i compatible SoCs
+
+maintainers:
+  - Wilken Gottwalt <wilken.gottwalt@posteo.net>
+
+description:
+  The hardware unit provides semaphores between the ARM cores and the embedded
+  companion core on the SoC.
+
+properties:
+  compatible:
+    const: allwinner,sun6i-a31-hwspinlock
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  resets:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - resets
+
+additionalProperties: false
+
+examples:
+  - |
+    hwlock@1c18000 {
+        compatible = "allwinner,sun6i-a31-hwspinlock";
+        reg = <0x01c18000 0x1000>;
+        clocks = <&ccu CLK_BUS_SPINLOCK>;
+        resets = <&ccu RST_BUS_SPINLOCK>;
+    };
+...