[muji/master] clarify how requesting streams works

[Dafydd Harries]

---
 xep/mingle.xml |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/xep/mingle.xml b/xep/mingle.xml
index af8ae4e..d5ffdc5 100644
--- a/xep/mingle.xml
+++ b/xep/mingle.xml
@@ -49,6 +49,13 @@ definitions of the content that they provide in their MUC presence. This is
 used to build a global payload type (PT) mapping for the various contents,
 which is then used to initiate normal Jingle sessions. The global mapping
 allows each participant to encode and payload each content only once.
+
+Participants can participate in a read-only mode by not advertising any
+contents. Participants are not obliged to initiate Jingle sessions with all
+other participants. If they do initiate a Jingle session with another
+participant, they are not required to accept all the contents that are
+available. For example, a Mingle client might choose to only request audio
+streams.
 </section1>
 
 <section1 topic='Starting a conference' anchor='starting'>
-- 
1.5.6.5