libcamera: properties: Provide a Devices camera property

Provide a new Camera property that allows pipeline handlers to list any
kernel device used to operate the camera. This allows other frameworks
and daemons such as PipeWire to better understand the resources consumed
by a Camera and consider ignoring those resources when enumerating
camera devices on a system.

Tested-by: Ashok Sidipotu <ashok.sidipotu@collabora.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/property_ids.yaml

@@ -690,6 +690,16 @@ controls:
         that is twice that of the full resolution mode. This value will be valid
         after the configure method has returned successfully.
 
+  - SystemDevices:
+      type: int64_t
+      size: [n]
+      description: |
+        A list of integer values of type dev_t denoting the major and minor
+        device numbers of the underlying devices used in the operation of this
+        camera.
+
+        Different cameras may report identical devices.
+
   # ----------------------------------------------------------------------------
   # Draft properties section