[PATCH v3 2/3] dt-bindings: iio: light: isl29018: add isil,cover-comp-gain

[Herman van Hazendonk <github.com@herrie.org>]

Document the new optional property that seeds the ISL29018 calibration
scale factor at boot from firmware, allowing boards with tinted cover
glass to ship with correct luminance readings without a userspace helper.

The value is a positive integer (minimum 1, maximum 65535) that is
multiplied with the raw lux reading.  Userspace can still override it
at runtime through in_illuminance0_calibscale.

Signed-off-by: Herman van Hazendonk <github.com@herrie.org>
---
 .../devicetree/bindings/iio/light/isl29018.yaml     | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/light/isl29018.yaml b/Documentation/devicetree/bindings/iio/light/isl29018.yaml
index 0ea278b07d1c..92ea2742bbd3 100644
--- a/Documentation/devicetree/bindings/iio/light/isl29018.yaml
+++ b/Documentation/devicetree/bindings/iio/light/isl29018.yaml
@@ -34,6 +34,19 @@ properties:
   vcc-supply:
     description: Regulator that provides power to the sensor
 
+  isil,cover-comp-gain:
+    description: |
+      Multiplier applied to the ambient-light reading at startup to
+      compensate for optical loss in the board's cover glass. Boards
+      that mount the sensor under a tinted or coated window typically
+      need a value between a few and a few hundred. The value seeds
+      in_illuminance0_calibscale, so it can still be retuned at
+      runtime through sysfs.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 65535
+    default: 1
+
 required:
   - compatible
   - reg
-- 
2.43.0