[CE-249] Update Cello with Release Process

This PR is aimed to update cello-rtd with the release
process.

Change-Id: Icf4cb7d62f8a70681ef7edcf97e8812dccca2df7
Signed-off-by: Krishna Harsha Voora <[email protected]>

docs/release_process.md

@@ -0,0 +1,41 @@
+# Release Process Document
+
+Below is the detailed plan on the Hyperledger Cello Release process, namely the steps taken to
+publish docker images.
+
+On the release day a maintainer submits a patch set to the hyperledger/cello repository to trigger
+the release process by changing the following variables in the Makefile - ``IS_RELEASE = TRUE``,
+``BASE_VERSION`` and ``PREVIOUS_VERSION`` - to the appropriate versions.
+
+CI triggers the cello-verify-x86_64 jobs and returns **SUCCESS (+1)**
+or **FAILURE (-1)** results (gerrit voting) back to the gerrit patch set commit. After approving
+the successful patch, maintainers merge the patch.
+
+Upon notification of the successful merge, the Release Engineer creates a "Release Tag" in the
+hyperledger/cello repository which in turn kicks off the Build Process and CI (Jenkins) triggers
+release jobs (listed below) based on the newly created "Release Tag".
+
+![Release_CI](./imgs/Release_CI.png)
+
+**Release Process from CI**:
+
+As part of the release process, CI automatically triggers the following release jobs after a
+"Release Tag" is created in each repository:
+
+- **Publish Fabric Docker images**:
+
+CI triggers release jobs on two platforms (**s390x and ppc64le**) and for **x86_64** configured to be
+auto published from dockerhub auto-build, upon successful run, publishes Docker images (*cello-mongo, cello-nginx, cello-baseimage*) to the
+[(https://hub.docker.com/u/hyperledger/)](https://hub.docker.com/u/hyperledger/ "Hyperledger Docker Hub") account.
+
+- cello-release-ppc64le
+- cello-release-s390x
+
+What happens?:
+
+- Release job executes `make docker` and builds docker images. The job then calls `make install`
+which in-turn will publish the docker images to the Hyperledger Docker Hub account.
+
+- Each image is then tagged as follows:
+
+     hyperledger/componentname:ARCH_Name-BASE_VERSION ex: (hyperledger/cello-baseimage:ppc64le-v0.8.0-alpha)