dt-bindings: backlight: Add lm3630a bindings

Add new backlight bindings for the TI LM3630A dual-string white LED.
Signed-off-by: Brian Masney <masneyb@onstation.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/leds/backlight/lm3630a-backlight.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/lm3630a-backlight.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TI LM3630A High-Efficiency Dual-String White LED
+
+maintainers:
+  - Lee Jones <lee.jones@linaro.org>
+  - Daniel Thompson <daniel.thompson@linaro.org>
+  - Jingoo Han <jingoohan1@gmail.com>
+
+description: |
+  The LM3630A is a current-mode boost converter which supplies the power and
+  controls the current in up to two strings of 10 LEDs per string.
+  https://www.ti.com/product/LM3630A
+
+properties:
+  compatible:
+    const: ti,lm3630a
+
+  reg:
+    maxItems: 1
+
+  ti,linear-mapping-mode:
+    description: |
+      Enable linear mapping mode. If disabled, then it will use exponential
+      mapping mode in which the ramp up/down appears to have a more uniform
+      transition to the human eye.
+    type: boolean
+
+required:
+  - compatible
+  - reg
+
+patternProperties:
+  "^led@[01]$":
+    type: object
+    description: |
+      Properties for a string of connected LEDs.
+
+    properties:
+      reg:
+        description: |
+          The control bank that is used to program the two current sinks. The
+          LM3630A has two control banks (A and B) and are represented as 0 or 1
+          in this property. The two current sinks can be controlled
+          independently with both banks, or bank A can be configured to control
+          both sinks with the led-sources property.
+        maxItems: 1
+        minimum: 0
+        maximum: 1
+
+      label:
+        maxItems: 1
+
+      led-sources:
+        allOf:
+          - minItems: 1
+            maxItems: 2
+            items:
+              minimum: 0
+              maximum: 1
+
+      default-brightness:
+        description: Default brightness level on boot.
+        minimum: 0
+        maximum: 255
+
+      max-brightness:
+        description: Maximum brightness that is allowed during runtime.
+        minimum: 0
+        maximum: 255
+
+    required:
+      - reg
+
+    additionalProperties: false
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        led-controller@38 {
+                compatible = "ti,lm3630a";
+                reg = <0x38>;
+
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                led@0 {
+                        reg = <0>;
+                        led-sources = <0 1>;
+                        label = "lcd-backlight";
+                        default-brightness = <200>;
+                        max-brightness = <255>;
+                };
+        };
+    };
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        led-controller@38 {
+                compatible = "ti,lm3630a";
+                reg = <0x38>;
+
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                led@0 {
+                        reg = <0>;
+                        default-brightness = <150>;
+                        ti,linear-mapping-mode;
+                };
+
+                led@1 {
+                        reg = <1>;
+                        default-brightness = <225>;
+                        ti,linear-mapping-mode;
+                };
+        };
+    };