dt-bindings: reset: st,sti-powerdown: Convert to yaml

Convert the device tree bindings for the STMicroelectronics STi
Peripheral Powerdown reset controller to YAML schema to allow
participating in DT validation.

Signed-off-by: Philipp Zabel <[email protected]>
Cc: Srinivas Kandagatla <[email protected]>
Reviewed-by: Rob Herring <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Documentation/devicetree/bindings/reset/st,stih407-powerdown.yaml

@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/reset/st,stih407-powerdown.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: STMicroelectronics STi family Sysconfig Peripheral Powerdown Reset Controller
+
+maintainers:
+  - Srinivas Kandagatla <[email protected]>
+
+description: |
+  This binding describes a reset controller device that is used to enable and
+  disable on-chip peripheral controllers such as USB and SATA, using
+  "powerdown" control bits found in the STi family SoC system configuration
+  registers. These have been grouped together into a single reset controller
+  device for convenience.
+
+  The actual action taken when powerdown is asserted is hardware dependent.
+  However, when asserted it may not be possible to access the hardware's
+  registers and after an assert/deassert sequence the hardware's previous state
+  may no longer be valid.
+
+properties:
+  compatible:
+    const: st,stih407-powerdown
+
+  '#reset-cells':
+    const: 1
+
+required:
+  - compatible
+  - '#reset-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/reset/stih407-resets.h>
+
+    powerdown: powerdown-controller {
+        compatible = "st,stih407-powerdown";
+        #reset-cells = <1>;
+    };
+
+    // Specifying powerdown control of devices:
+    st_dwc3: dwc3 {
+        resets = <&powerdown STIH407_USB3_POWERDOWN>;
+    };