doc/developer: add "Adding files to the fate-suite dataset"

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/developer.texi

@@ -533,4 +533,16 @@ Running 'make fate' accomplishes this, please see @url{fate.html} for details.
 this case, the reference results of the regression tests shall be modified
 accordingly].
 
+@subsection Adding files to the fate-suite dataset
+
+When there is no muxer or encoder available to generate test media for a
+specific test then the media has to be inlcuded in the fate-suite.
+First please make sure that the sample file is as small as possible to test the
+respective decoder or demuxer sufficiently. Large files increase network
+bandwidth and disk space requirements.
+Once you have a working fate test and fate sample, provide in the commit
+message or introductionary message for the patch series that you post to
+the ffmpeg-devel mailing list, a direct link to download the sample media.
+
+
 @bye