Replace TOPDIR with OSMO_GSM_MANUALS_DIR. When the project specific
manuals will be built out of this repository, we still need to refer to
the top directory of the shared content. But it will be in another
repository, so we need to rename the variable to avoid confusion.
(moving manuals to project repositories 3/19)
Related: OS#3385
Change-Id: I2af797546de048a6ab19a5cbc755e5e15575d7ab
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