Documentation: bindings: clk: Add bindings for i.MX BLK_CTL

Document the i.MX BLK_CTL with its devicetree properties.

Signed-off-by: Abel Vesa <abel.vesa@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/fsl,imx-blk-ctl.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/fsl,imx-blk-ctl.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP i.MX BLK_CTL
+
+maintainers:
+  - Abel Vesa <abel.vesa@nxp.com>
+
+description:
+  i.MX BLK_CTL is a conglomerate of different GPRs that are
+  dedicated to a specific subsystem. Because it usually contains
+  clocks amongst other things, it needs access to the i.MX clocks
+  API. All the other functionalities it provides can work just fine
+  from the clock subsystem tree.
+
+properties:
+  compatible:
+    items:
+      - enum:
+         - fsl,imx8mp-audio-blk-ctl
+         - fsl,imx8mp-hdmi-blk-ctl
+         - fsl,imx8mp-media-blk-ctl
+      - const: syscon
+
+  reg:
+    maxItems: 1
+
+  power-domains:
+    maxItems: 1
+
+  '#clock-cells':
+    const: 1
+
+  '#reset-cells':
+    const: 1
+
+required:
+  - compatible
+  - reg
+  - power-domains
+  - '#clock-cells'
+  - '#reset-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/imx8mp-clock.h>
+
+    audio_blk_ctl: clock-controller@30e20000 {
+       compatible = "fsl,imx8mp-audio-blk-ctl", "syscon";
+       reg = <0x30e20000 0x10000>;
+       power-domains = <&audiomix_pd>;
+
+       #clock-cells = <1>;
+       #reset-cells = <1>;
+    };