V4L/DVB (12761): DocBook: add media API specs

The V4L and DVB API's are there for a long time. however, up to now,
no efforts were done to merge them to kernel DocBook.

This patch adds the current versions of the specs as an unique compendium.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/v4l/dev-teletext.xml

@@ -0,0 +1,40 @@
+  <title>Teletext Interface</title>
+
+  <para>This interface aims at devices receiving and demodulating
+Teletext data [<xref linkend="ets300706" />, <xref linkend="itu653" />], evaluating the
+Teletext packages and storing formatted pages in cache memory. Such
+devices are usually implemented as microcontrollers with serial
+interface (I<superscript>2</superscript>C) and can be found on older
+TV cards, dedicated Teletext decoding cards and home-brew devices
+connected to the PC parallel port.</para>
+
+  <para>The Teletext API was designed by Martin Buck. It is defined in
+the kernel header file <filename>linux/videotext.h</filename>, the
+specification is available from <ulink url="http://home.pages.de/~videotext/">
+http://home.pages.de/~videotext/</ulink>. (Videotext is the name of
+the German public television Teletext service.) Conventional character
+device file names are <filename>/dev/vtx</filename> and
+<filename>/dev/vttuner</filename>, with device number 83, 0 and 83, 16
+respectively. A similar interface exists for the Philips SAA5249
+Teletext decoder [specification?] with character device file names
+<filename>/dev/tlkN</filename>, device number 102, N.</para>
+
+  <para>Eventually the Teletext API was integrated into the V4L API
+with character device file names <filename>/dev/vtx0</filename> to
+<filename>/dev/vtx31</filename>, device major number 81, minor numbers
+192 to 223. For reference the V4L Teletext API specification is
+reproduced here in full: "Teletext interfaces talk the existing VTX
+API." Teletext devices with major number 83 and 102 will be removed in
+Linux 2.6.</para>
+
+  <para>There are no plans to replace the Teletext API or to integrate
+it into V4L2. Please write to the linux-media mailing list: &v4l-ml;
+when the need arises.</para>
+
+  <!--
+Local Variables:
+mode: sgml
+sgml-parent-document: "v4l2.sgml"
+indent-tabs-mode: nil
+End:
+  -->