Introduce chapter trx_if.adoc and add it to OsmoTRX and OsmoBTS

This chapter defines the protocol used between osmo-trx and
osmo-bts-trx.

Most of the text comes originally from osmo-trx.git/README, as it's the
only known documentation of the protocol other than the code itself.

Change-Id: I56c418eef0f826ae1aadbed5b151fbed241c7885
1 file changed
tree: 57c7d52100baadb715bf1df9e89ebaa483102503
  1. doc/