OpenAirUsage.md

@@ -25,6 +25,7 @@
 * [How to setup OAI with Lime SDR](how-to-setup-oai-with-lmsdr)
 * [nFAPI introduction and HowTo](nFAPI-howto)
 * [Multiple PLMNs/S1-flex/NNSF](s1-flex-conf-nnsf)
+* [The F1 CU-DU split](f1-interface)
 
 ## UE tutorial