Update README to cover osmo-gbproxy and not osmo-sgsn

While we're at it, also convert it to markdown.

Related: OS#4992
Change-Id: Ic7e86dfed985f98ae87af9adcde6f776c5a15044

README

@@ -1,17 +0,0 @@
-About OsmoSGSN
-==============
-
-OsmoSGSN originated from the OpenBSC project, as a separate program within
-openbsc.git. In 2017, OpenBSC was split in separate repositories, and hence
-OsmoSGSN was given its own separate git repository.
-
-OsmoSGSN exposes
-- GSUP towards OsmoHLR (or a MAP proxy);
-- GTP towards a GGSN (e.g. OsmoGGSN);
-- Gb towards a BSS (e.g. OsmoPCU);
-- IuPS towards an RNC or HNB-GW (e.g. OsmoHNBGW) for 3G data;
-- The Osmocom typical telnet VTY and CTRL interfaces.
-
-Find OsmoSGSN issue tracker and wiki online at
-https://osmocom.org/projects/osmosgsn
-https://osmocom.org/projects/osmosgsn/wiki

README.md

@@ -0,0 +1,28 @@
+About osmo-gbproxy
+==================
+
+osmo-gbproxy is a proxy for the Gb interface within the 3GPP GERAN (GPRS/EDGE RAN)
+architecture. It is part of the [Osmocom](https://osmocom.org/) Open Source
+Mobile Communications projects.
+
+It allows you to aggregate many Gb links/connections into one. It also
+has the ability to convert between different Gb interface protocol
+stacking, such as from Gb-over-FrameRelay to Gb-over-IP.
+
+Until 2021 it used to be part of the osmo-sgsn git repository, and before that
+(until 2017) part of openbsc.git
+
+Homepage and Issue Tracker
+--------------------------
+
+Find the issue tracker and wiki online at
+<https://osmocom.org/projects/osmo-gbproxy> and
+<https://osmocom.org/projects/osmo-gbproxy/wiki>, respectively.
+
+Documentation
+-------------
+
+You can find the user manual at
+<https://ftp.osmocom.org/docs/latest/osmogbproxy-usermanual.pdf>
+and the VTY reference manual at
+<https://ftp.osmocom.org/docs/latest/osmogbproxy-vty-reference.pdf>.

contrib/osmo-gbproxy.spec.in

@@ -68,7 +68,7 @@ make %{?_smp_mflags}
 make %{?_smp_mflags} check || (find . -name testsuite.log -exec cat {} +)
 
 %files
-%doc AUTHORS README
+%doc AUTHORS README.md
 %dir %{_docdir}/%{name}/examples
 %dir %{_docdir}/%{name}/examples/osmo-sgsn
 %{_docdir}/%{name}/examples/osmo-sgsn/osmo-gbproxy.cfg

debian/copyright

@@ -7,7 +7,7 @@ Files:     .gitignore
            .mailmap
            AUTHORS
            Makefile.am
-           README
+           README.md
            README.vty-tests
            configure.ac
            contrib/Makefile.am