Add README.md to explain what this is all about

Change-Id: Idb8b7ac9ee93e93971376644444e434c41aa18fa
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A README.md
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+libasn1c - shared library of asn1c runtime
+==========================================
+
+This repository contains a shared library built from the asn1c runtime files.
+
+Normally, the upstream asn1c copies an identical set of source code files into each and every project using
+asn1c.  This becomes problematic if a single program uses multiple different ASN.1 specifications, where then
+those source files would clash.
+
+Let's instead move those runtime files into a shared library (*libasn1c*), which is then linked once by each program
+needing it, no matter how many asn1c-generated specifications/syntax it uses.
+
+**The version of the asn1c compiler must match the version of libasn1c**.  We are using this shared library in
+combination with the [osmocom fork of asn1c](https://gitea.osmocom.org/osmocom/asn1c).
+
+
+GIT Repository
+--------------
+
+You can clone from the official libosmocore.git repository using
+
+	git clone https://gitea.osmocom.org/cellular-infrastructure/libasn1c
+
+There is a web interface at <https://gitea.osmocom.org/cellular-infrastructure/libasn1c>
+
+
+Mailing List
+------------
+
+Discussions related to libasn1c are happening on the
+openbsc@lists.osmocom.org mailing list, please see
+<https://lists.osmocom.org/mailman/listinfo/openbsc> for subscription
+options and the list archive.
+
+Please observe the [Osmocom Mailing List
+Rules](https://osmocom.org/projects/cellular-infrastructure/wiki/Mailing_List_Rules)
+when posting.

