[media] DocBook: Improve DVB frontend description

The DVB frontend API got bitrotten. Update it.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

Documentation/DocBook/media/dvb/frontend.xml

 <title>DVB Frontend API</title>
 
-<para>The DVB frontend device controls the tuner and DVB demodulator
-hardware. It can be accessed through <emphasis
-role="bold">/dev/dvb/adapter0/frontend0</emphasis>. Data types and and
-ioctl definitions can be accessed by including <emphasis
-role="bold">linux/dvb/frontend.h</emphasis> in your application.</para>
-
-<para>DVB frontends come in three varieties: DVB-S (satellite), DVB-C
-(cable) and DVB-T (terrestrial). Transmission via the internet (DVB-IP)
-is not yet handled by this API but a future extension is possible. For
-DVB-S the frontend device also supports satellite equipment control
-(SEC) via DiSEqC and V-SEC protocols. The DiSEqC (digital SEC)
-specification is available from
-<ulink url="http://www.eutelsat.com/satellites/4_5_5.html">Eutelsat</ulink>.</para>
+<para>The DVB frontend API was designed to support three types of delivery systems:</para>
+<itemizedlist>
+    <listitem>Terrestrial systems: DVB-T, DVB-T2, ATSC, ATSC M/H, ISDB-T, DVB-H, DTMB, CMMB</listitem>
+    <listitem>Cable systems: DVB-C Annex A/C, ClearQAM (DVB-C Annex B), ISDB-C</listitem>
+    <listitem>Satellital systems: DVB-S, DVB-S2, DVB Turbo, ISDB-S, DSS</listitem>
+</itemizedlist>
+<para>The DVB frontend controls several sub-devices including:</para>
+<itemizedlist>
+    <listitem>Tuner</listitem>,
+    <listitem>Digital TV demodulator</listitem>
+    <listitem>Low noise amplifier (LNA)</listitem>
+    <listitem>Satellite Equipment Control (SEC) hardware (only for Satellite).</listitem>
+</itemizedlist>
+<para>The frontend can be accessed through
+    <emphasis role="bold">/dev/dvb/adapter?/frontend?</emphasis>. Data types and
+    ioctl definitions can be accessed by including
+    <emphasis role="bold">linux/dvb/frontend.h</emphasis> in your application.
+</para>
 
-<para>Note that the DVB API may also be used for MPEG decoder-only PCI
-cards, in which case there exists no frontend device.</para>
+<para>NOTE: Transmission via the internet (DVB-IP)
+    is not yet handled by this API but a future extension is possible.</para>
+<para>On Satellital systems, the API support for the Satellite Equipment Control
+    (SEC) allows to power control and to send/receive signals to control the
+    antenna subsystem, selecting the polarization and choosing the Intermediate
+    Frequency IF) of the Low Noise Block Converter Feed Horn (LNBf). It
+    supports the DiSEqC and V-SEC protocols. The DiSEqC (digital SEC)
+specification is available at
+<ulink url="http://www.eutelsat.com/satellites/4_5_5.html">Eutelsat</ulink>.</para>
 
 <section id="frontend_types">
 <title>Frontend Data Types</title>
@@ -23,8 +35,8 @@ cards, in which case there exists no frontend device.</para>
 <section id="fe-type-t">
 <title>Frontend type</title>
 
-<para>For historical reasons, frontend types are named by the type of modulation used in
-transmission. The fontend types are given by fe_type_t type, defined as:</para>
+<para>For historical reasons, frontend types are named by the type of modulation
+    used in transmission. The fontend types are given by fe_type_t type, defined as:</para>
 
 <table pgwide="1" frame="none" id="fe-type">
 <title>Frontend types</title>