dt-bindings: backlight: Add Texas Instruments LM3509

Add Device Tree bindings for Texas Instruments LM3509 - a
High Efficiency Boost for White LED's and/or OLED Displays
Signed-off-by: Patrick Gansterer <paroga@paroga.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240526105136.721529-2-paroga@paroga.comSigned-off-by: Lee Jones <lee@kernel.org>

Documentation/devicetree/bindings/leds/backlight/ti,lm3509.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/ti,lm3509.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TI LM3509 High Efficiency Boost for White LED's and/or OLED Displays
+
+maintainers:
+  - Patrick Gansterer <paroga@paroga.com>
+
+description:
+  The LM3509 current mode boost converter offers two separate outputs.
+  https://www.ti.com/product/LM3509
+
+properties:
+  compatible:
+    const: ti,lm3509
+
+  reg:
+    maxItems: 1
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+  reset-gpios:
+    maxItems: 1
+
+  ti,brightness-rate-of-change-us:
+    description: Brightness Rate of Change in microseconds.
+    enum: [51, 13000, 26000, 52000]
+
+  ti,oled-mode:
+    description: Enable OLED mode.
+    type: boolean
+
+patternProperties:
+  "^led@[01]$":
+    type: object
+    description: Properties for a string of connected LEDs.
+    $ref: common.yaml#
+
+    properties:
+      reg:
+        description:
+          The control register that is used to program the two current sinks.
+          The LM3509 has two registers (BMAIN and BSUB) and are represented
+          as 0 or 1 in this property. The two current sinks can be controlled
+          independently with both registers, or register BMAIN can be
+          configured to control both sinks with the led-sources property.
+        minimum: 0
+        maximum: 1
+
+      label: true
+
+      led-sources:
+        minItems: 1
+        maxItems: 2
+        items:
+          minimum: 0
+          maximum: 1
+
+      default-brightness:
+        minimum: 0
+        maximum: 31
+        default: 18
+
+      max-brightness:
+        minimum: 0
+        maximum: 31
+        default: 31
+
+    required:
+      - reg
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        backlight@36 {
+            compatible = "ti,lm3509";
+            reg = <0x36>;
+            reset-gpios = <&gpio2 5 GPIO_ACTIVE_LOW>;
+
+            ti,oled-mode;
+            ti,brightness-rate-of-change-us = <52000>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            led@0 {
+                reg = <0>;
+                led-sources = <0 1>;
+                label = "lcd-backlight";
+                default-brightness = <12>;
+                max-brightness = <31>;
+            };
+        };
+    };
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        backlight@36 {
+            compatible = "ti,lm3509";
+            reg = <0x36>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            led@0 {
+                reg = <0>;
+                default-brightness = <12>;
+            };
+
+            led@1 {
+                reg = <1>;
+                default-brightness = <15>;
+            };
+        };
+    };