Hi Rob,

... 

quoted

 .../bindings/leds/backlight/mps,mp3309c.yaml  | 82
+++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644
Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml

diff --git
a/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml
b/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yaml
new file mode 100644
index 000000000000..e2f9ae2b3fb4

--- /dev/null
+++

b/Documentation/devicetree/bindings/leds/backlight/mps,mp3309c.yam

quoted

+++ l

@@ -0,0 +1,82 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) %YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/mps,mp3309c.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: MPS MP3309C backlight
+
+maintainers:
+  - Flavio Suligoi <f.suligoi@asem.it>
+
+description: |
+  The Monolithic Power (MPS) MP3309C is a WLED step-up converter,
+featuring a
+  programmable switching frequency to optimize efficiency.
+  It supports two different dimming modes:
+
+  - analog mode, via I2C commands, as default mode (32 dimming
+ levels)
+  - PWM controlled mode (optional)
+
+  The datasheet is available at:
+  https://www.monolithicpower.com/en/mp3309c.html
+
+properties:
+  compatible:
+    const: mps,mp3309c
+
+  reg:
+    maxItems: 1
+
+  pwms:
+    description: if present, the backlight is controlled in PWM mode.
+    maxItems: 1
+
+  enable-gpios:
+    description: GPIO used to enable the backlight in "analog-i2c" dimming

mode.

quoted

+    maxItems: 1
+
+  brightness-levels:
+    description:
+      Array of distinct brightness levels, in PWM dimming mode.
+      Typically these are in the range from 0 to 255, but any range starting
+      at 0 will do.
+      The 0 value means a 0% duty cycle (darkest/off), while the last value in
+      the array represents a 100% duty cycle (brightest).
+    $ref: /schemas/types.yaml#/definitions/uint32-array

This already has a type defined. Please add it to backlight/common.yaml and
remove from led-backlight.yaml and pwm-backlight.yaml.

Ok, I'll add common.yaml and I'll prepare two other separate patches for these.

You say 0-255 here, but your example is 0-10. One of those seems wrong.
Anyways, don't define constraints in prose, use a schema:

items:
  maximum: 10 (or 255?)

Ok, I'll add maximum, and I'll change the example, using 0..255

quoted

+
+  default-brightness:
+    description:
+      The default brightness (index into the levels array).
+    $ref: /schemas/types.yaml#/definitions/uint32

Already has a type. You need to reference backlight/common.yaml.

Ok

quoted

+
+  mps,overvoltage-protection-microvolt:
+    description: Overvoltage protection (13.5V, 24V or 35.5V).
+    enum: [ 13500000, 24000000, 35500000 ]
+    default: 35500000
+
+  mps,no-sync-mode:
+    description: disable synchronous rectification mode
+    type: boolean
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        /* Backlight with PWM control */
+        backlight_pwm: backlight@17 {
+            compatible = "mps,mp3309c";
+            reg = <0x17>;
+            pwms = <&pwm1 0 3333333 0>; /* 300 Hz --> (1/f) * 1*10^9 */
+            brightness-levels = <0 1 2 3 4 5 6 7 8 9 10>;
+            default-brightness = <8>;
+            mps,overvoltage-protection-microvolt = <24000000>;
+        };
+    };
--
2.34.1

Thanks,
Flavio