[media] DocBook: document RF tuner bandwidth controls

Add documentation for RF tuner bandwidth controls. These controls are
used to set filters on tuner signal path.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

Documentation/DocBook/media/v4l/controls.xml

@@ -5043,6 +5043,25 @@ of devices having RF tuner.</para>
             </row><row><entry spanname="descr">The RF_TUNER class
 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
 description of this control class.</entry>
+            </row>
+            <row>
+              <entry spanname="id"><constant>V4L2_CID_RF_TUNER_BANDWIDTH_AUTO</constant>&nbsp;</entry>
+              <entry>boolean</entry>
+            </row>
+            <row>
+              <entry spanname="descr">Enables/disables tuner radio channel
+bandwidth configuration. In automatic mode bandwidth configuration is performed
+by the driver.</entry>
+            </row>
+            <row>
+              <entry spanname="id"><constant>V4L2_CID_RF_TUNER_BANDWIDTH</constant>&nbsp;</entry>
+              <entry>integer</entry>
+            </row>
+            <row>
+              <entry spanname="descr">Filter(s) on tuner signal path are used to
+filter signal according to receiving party needs. Driver configures filters to
+fulfill desired bandwidth requirement. Used when V4L2_CID_RF_TUNER_BANDWIDTH_AUTO is not
+set. The range and step are driver-specific.</entry>
             </row>
             <row>
               <entry spanname="id"><constant>V4L2_CID_RF_TUNER_LNA_GAIN_AUTO</constant>&nbsp;</entry>