Backport README update to 2.12 branch

Author: cowtowncoder

README.md

@@ -1,25 +1,81 @@
-## Overview
+# Overview
 
 This is a multi-module umbrella project for [Jackson](../../../jackson)
 standard binary dataformat backends.
 
-Currently included are:
+Dataformat backends are used to support format alternatives to JSON, using
+general-purpose Jackson  API. Formats included allow access using all 3
+API styles (streaming, databinding, tree model).
 
-* [Avro](avro/)
-* [CBOR](cbor/)
-* [Ion](ion/)
-* [Protobuf](protobuf/)
-* [Smile](smile/)
+For Jackson 2.x this is done by sub-classing Jackson core abstractions of:
 
-## License
+* All backends sub-class `JsonFactory`, which is factory for:
+    * `JsonParser` for reading data (decoding data encoding in supported format)
+    * `JsonGenerator` for writing data (encoding data using supported format)
+* Starting with 2.10 there is also sub-class of `ObjectMapper` (like `CBORMapper`, `SmileMapper`) for all formats, mostly for convenience
+* Jackson 2.10 also added "Builder" style construction for above-mentioned factories, mappers.
+
+# Status
+
+[![Build Status](https://travis-ci.org/FasterXML/jackson-dataformats-binary.svg)](https://travis-ci.org/FasterXML/jackson-dataformats-binary)
+
+# Binary formats supported
+
+Currently included backends are:
+
+* [Avro](avro/) ([Avro format](http://avro.apache.org/docs/current))
+* [CBOR](cbor/) ([CBOR format](https://tools.ietf.org/html/rfc7049))
+* [Ion](ion/) ([Ion format](https://amznlabs.github.io/ion-docs/))
+* [Protobuf](protobuf/) ([Protobuf format](https://developers.google.com/protocol-buffers/))
+* [Smile](smile/) ([Smile format](https://github.com/FasterXML/smile-format-specification))
+
+# License
 
 All modules are licensed under [Apache License 2.0](http://www.apache.org/licenses/LICENSE-2.0.txt).
 
-## Status
+# Maven dependencies
 
-[![Build Status](https://travis-ci.org/FasterXML/jackson-dataformats-binary.svg)](https://travis-ci.org/FasterXML/jackson-dataformats-binary)
+To use these format backends Maven-based projects, use following dependency:
+
+```xml
+<dependency>
+  <groupId>com.fasterxml.jackson.dataformat</groupId>
+  <artifactId>jackson-dataformat-[FORMAT]</artifactId>
+  <version>2.12.2</version>
+</dependency>
+```
+
+where `[FORMAT]` is one of supported modules (`avro`, `cbor`, `smile` etc)
+
+# Development
+
+## Maintainers
+
+* Author: Tatu Saloranta (@cowtowncoder)
+* Active Maintainers:
+    * Michael Liedtke (@mcliedtke) (Ion backend)
+
+You may at-reference them as necessary but please keep in mind that all
+maintenance work is strictly voluntary (no one gets paid to work on this
+or any other Jackson components) so there is no guarantee for timeliness of
+responses.
+
+## Branches
+
+`master` branch is for developing the next major Jackson version -- 3.0 -- but there
+are active maintenance branches in which much of development happens:
+
+* `2.13` is for developing the next 2.x version
+* `2.12` and `2.11` are for backported fixes for 2.12/2.11 versions (respectively)
+
+
+Older branches are usually not changed but are available for historic reasons.
+All released versions have matching git tags (`jackson-dataformats-binary-2.10.3`).
+
+Note that since individual format modules used to live in their own repositories,
+older branches (before 2.8) and tags do not exist in this repository.
 
-## Other Jackson binary backends
+# Other Jackson binary backends
 
 In addition to binary format backends hosted by FasterXML in this repo, there are other
 known Jackson backends for binary data formats.
@@ -29,6 +85,6 @@ For example:
 * [EXIficient](https://github.com/EXIficient/exificient-for-json) for [Efficient XML Interchange](https://en.wikipedia.org/wiki/Efficient_XML_Interchange)
 * [jackson-dataformat-msgpack](https://github.com/msgpack/msgpack-java/tree/develop/msgpack-jackson) for [MessagePack](http://en.wikipedia.org/wiki/MessagePack) (aka `MsgPack`) format
 
-## More
+# More
 
 See [Wiki](../../wiki) for more information (javadocs).