Added overview documentation for the radio

Change-Id: I71b072512db51f23b0aed82545b504f9efc824d0
Reviewed-by: Dmytro Poplavskiy <dmytro.poplavskiy@nokia.com>

src/imports/multimedia/qdeclarativeradio.cpp

@@ -89,6 +89,8 @@ QT_BEGIN_NAMESPACE
 
     The corresponding \l RadioData element gives RDS information about the current radio station.
 
+    \sa {Radio Overview}
+
 */
 
 

src/imports/multimedia/qdeclarativeradiodata.cpp

@@ -93,6 +93,8 @@ QT_BEGIN_NAMESPACE
 
     You use \c RadioData together with the \l Radio element. The properties of the RadioData element will reflect the
     information broadcast by the radio station the Radio element is currently tuned to.
+
+    \sa {Radio Overview}
 */
 QDeclarativeRadioData::QDeclarativeRadioData(QObject *parent) :
     QObject(parent),