[RFC v3 5/9] media: Documentation: Add scaling and post-scaler crop for common raw

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Document scaling and post-scaler digital crop operations for the common
raw sensor model.
Signedg-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 .../media/v4l/subdev-config-model.rst         | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/Documentation/userspace-api/media/v4l/subdev-config-model.rst b/Documentation/userspace-api/media/v4l/subdev-config-model.rst
index 4ddf98e3143c..1ae20800f34b 100644
--- a/Documentation/userspace-api/media/v4l/subdev-config-model.rst
+++ b/Documentation/userspace-api/media/v4l/subdev-config-model.rst
@@ -119,9 +119,13 @@ The digital crop operation takes place after binning and sub-sampling. It is
 configured by setting the ``V4L2_SEL_TGT_CROP`` rectangle on (pad, stream) pair
 0/0. The resulting image size is further output by the sensor.
 
+The digital scaling operation is performed after the digital crop. It is
+configured by setting the ``V4L2_SEL_TGT_COMPOSE`` rectangle on (pad, stream) pair
+0/0, relative to the digital crop.
+
 The sensor's output mbus code is configured by setting the format on the (pad,
-stream) pair 0/0. When setting the format, always use the same width and height
-as for the digital crop setting.
+stream) pair 0/0. The width and height fields are used to configure post-scaler
+digital crop, affecting the right side and the bottom of the frame.
 
 Drivers may only support some of even none of these configurations, in which
 case they do not expose the corresponding selection rectangles. If any selection
@@ -179,12 +183,19 @@ Also refer to :ref:`Selection targets <v4l2-selection-targets-table>`.
       - X
       - Digital crop. This rectangle is relative to the ``V4L2_SEL_TGT_COMPOSE``
         rectangle on (pad, stream) pair 1/0.
+    * - 0/0
+      - ``V4L2_SEL_TGT_COMPOSE``
+      - \-
+      - X
+      - Scaling. This rectangle is relative to the ``V4L2_SEL_TGT_CROP``
+        rectangle on (pad, stream) pair 0/0.
     * - 0/0
       - Format
       - X
       - X
-      - Image data source format. Always assign the width and height fields of
-        the format to the same values than for the ``V4L2_SEL_TGT_CROP``
+      - Image data source format and post-scaler crop. The width and height
+        fields of the format, used to configure post-scaler crop on the right
+        and bottom edges of the image, are related to the ``V4L2_SEL_TGT_COMPOSE``
         rectangle on (pad, stream) pair 0/0. The media bus code reflects the
         pixel data output of the sensor.
     * - 0/1
-- 
2.39.5