diff --git a/Documentation/media/uapi/v4l/ext-ctrls-image-source.rst b/Documentation/media/uapi/v4l/ext-ctrls-image-source.rst
index 2c3ab5796d76..2d3e2b83d6dd 100644
--- a/Documentation/media/uapi/v4l/ext-ctrls-image-source.rst
+++ b/Documentation/media/uapi/v4l/ext-ctrls-image-source.rst
@@ -55,3 +55,13 @@ Image Source Control IDs
 
 ``V4L2_CID_TEST_PATTERN_GREENB (integer)``
     Test pattern green (next to blue) colour component.
+
+``V4L2_CID_UNIT_CELL_SIZE (struct)``
+    This control returns the unit cell size in nanometers. The struct
+    :c:type:`v4l2_area` provides the width and the height in separate
+    fields to take into consideration asymmetric pixels.
+    This control does not take into consideration any possible hardware
+    binning.
+    The unit cell consists of the whole area of the pixel, sensitive and
+    non-sensitive.
+    This control is required for automatic calibration of sensors/cameras.