dt-bindings: leds: backlight: Add Kinetic KTZ8866 backlight

Add Kinetic KTZ8866 backlight binding documentation.
Signed-off-by: Jianhua Lu <lujianhua000@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230120155018.15376-1-lujianhua000@gmail.com

Documentation/devicetree/bindings/leds/backlight/kinetic,ktz8866.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/kinetic,ktz8866.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Kinetic Technologies KTZ8866 backlight
+
+maintainers:
+  - Jianhua Lu <lujianhua000@gmail.com>
+
+description: |
+  The Kinetic Technologies KTZ8866 is a high efficiency 6-channels-current-sinks
+  led backlight with dual lcd bias power.
+  https://www.kinet-ic.com/ktz8866/
+
+allOf:
+  - $ref: common.yaml#
+
+properties:
+  compatible:
+    const: kinetic,ktz8866
+
+  vddpos-supply:
+    description: positive boost supply regulator.
+
+  vddneg-supply:
+    description: negative boost supply regulator.
+
+  enable-gpios:
+    description: GPIO to use to enable/disable the backlight (HWEN pin).
+    maxItems: 1
+
+  current-num-sinks:
+    description: number of the LED current sinks' channels.
+    enum: [1, 2, 3, 4, 5, 6]
+
+  kinetic,current-ramp-delay-ms:
+    description: |
+      LED current ramping delay time in milliseconds, note that the
+      case 1 will be mapped to 1μs.
+    enum: [1, 2, 4, 8, 16, 32, 64, 128, 192, 256, 320, 384, 448, 512, 576, 640]
+
+  kinetic,led-enable-ramp-delay-ms:
+    description: |
+      LED on/off ramping delay time in milliseconds, note that the case 0 will be
+      mapped to 512μs because ktz8866 can't ramp faster than it.
+    enum: [0, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384]
+
+  kinetic,enable-lcd-bias:
+    description: Set if we want to output bias power supply for LCD.
+    type: boolean
+
+required:
+  - compatible
+  - vddpos-supply
+  - vddneg-supply
+  - enable-gpios
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    backlight {
+        compatible = "kinetic,ktz8866";
+
+        vddpos-supply = <&bl_vddpos_5p5>;
+        vddneg-supply = <&bl_vddneg_5p5>;
+        enable-gpios = <&tlmm 139 GPIO_ACTIVE_HIGH>;
+        current-num-sinks = <5>;
+        kinetic,current-ramp-delay-ms = <128>;
+        kinetic,led-enable-ramp-delay-ms = <1>;
+        kinetic,enable-lcd-bias;
+    };