[media] DocBook: fix awkward language and fix the documented return value

The Video Standard section contains some awkward language. It also wasn't
updated when the error code for unimplemented ioctls changed from EINVAL
to ENOTTY.

[mchehab@redhat.com: remove a misplaced footnote tag]
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/media/v4l/common.xml

@@ -564,7 +564,7 @@ automatically.</para>
     <para>To query and select the standard used by the current video
 input or output applications call the &VIDIOC-G-STD; and
 &VIDIOC-S-STD; ioctl, respectively. The <emphasis>received</emphasis>
-standard can be sensed with the &VIDIOC-QUERYSTD; ioctl. Note parameter of all these ioctls is a pointer to a &v4l2-std-id; type (a standard set), <emphasis>not</emphasis> an index into the standard enumeration.<footnote>
+standard can be sensed with the &VIDIOC-QUERYSTD; ioctl. Note that the parameter of all these ioctls is a pointer to a &v4l2-std-id; type (a standard set), <emphasis>not</emphasis> an index into the standard enumeration.<footnote>
 	<para>An alternative to the current scheme is to use pointers
 to indices as arguments of <constant>VIDIOC_G_STD</constant> and
 <constant>VIDIOC_S_STD</constant>, the &v4l2-input; and
@@ -588,30 +588,28 @@ switch to a standard by &v4l2-std-id;.</para>
       </footnote> Drivers must implement all video standard ioctls
 when the device has one or more video inputs or outputs.</para>
 
-    <para>Special rules apply to USB cameras where the notion of video
-standards makes little sense. More generally any capture device,
-output devices accordingly, which is <itemizedlist>
+    <para>Special rules apply to devices such as USB cameras where the notion of video
+standards makes little sense. More generally for any capture or output device
+which is: <itemizedlist>
 	<listitem>
 	  <para>incapable of capturing fields or frames at the nominal
 rate of the video standard, or</para>
 	</listitem>
 	<listitem>
-	  <para>where <link linkend="buffer">timestamps</link> refer
-to the instant the field or frame was received by the driver, not the
-capture time, or</para>
-	</listitem>
-	<listitem>
-	  <para>where <link linkend="buffer">sequence numbers</link>
-refer to the frames received by the driver, not the captured
-frames.</para>
+	  <para>that does not support the video standard formats at all.</para>
 	</listitem>
       </itemizedlist> Here the driver shall set the
 <structfield>std</structfield> field of &v4l2-input; and &v4l2-output;
-to zero, the <constant>VIDIOC_G_STD</constant>,
+to zero and the <constant>VIDIOC_G_STD</constant>,
 <constant>VIDIOC_S_STD</constant>,
 <constant>VIDIOC_QUERYSTD</constant> and
 <constant>VIDIOC_ENUMSTD</constant> ioctls shall return the
-&EINVAL;.<footnote>
+&ENOTTY;.<footnote>
+	<para>See <xref linkend="buffer" /> for a rationale.</para>
+	<para>Applications can make use of the <xref linkend="input-capabilities" /> and
+<xref linkend="output-capabilities"/> flags to determine whether the video standard ioctls
+are available for the device.</para>
+&ENOTTY;.
 	<para>See <xref linkend="buffer" /> for a rationale. Probably
 even USB cameras follow some well known video standard. It might have
 been better to explicitly indicate elsewhere if a device cannot live
@@ -626,9 +624,9 @@ up to normal expectations, instead of this exception.</para>
 &v4l2-standard; standard;
 
 if (-1 == ioctl (fd, &VIDIOC-G-STD;, &amp;std_id)) {
-	/* Note when VIDIOC_ENUMSTD always returns EINVAL this
+	/* Note when VIDIOC_ENUMSTD always returns ENOTTY this
 	   is no video device or it falls under the USB exception,
-	   and VIDIOC_G_STD returning EINVAL is no error. */
+	   and VIDIOC_G_STD returning ENOTTY is no error. */
 
 	perror ("VIDIOC_G_STD");
 	exit (EXIT_FAILURE);