OCPBUGS-36641: Add documentation for versioning and branching (#122)

- Documents the versioning model, repository branch organization, OLM channels, OpenShift compatibility, and support model.
- Aims to guide users on selecting the appropriate ALBO version for their OpenShift environment.

README.md

@@ -21,6 +21,7 @@ describes the design and implementation of the operator in more detail.
     3. [Running the end-to-end tests](#running-the-end-to-end-tests)
     4. [Running the end-to-end tests on an STS cluster](#running-the-end-to-end-tests-on-an-sts-cluster)
 5. [Proxy support](#proxy-support)
+6. [Versioning](docs/versioning.md)
 
 ## Local Development
 

docs/versioning.md

@@ -0,0 +1,48 @@
+# Versioning and Branching in AWS Load Balancer Operator
+
+The AWS Load Balancer Operator follows the semantic versioning, for any given release `X.Y.Z`:
+* an X (major) release indicates a set of backwards-compatible changes. Changing X means there's a breaking change.
+* a Y (minor) release indicates a minimum feature set. Changing Y means the addition of a backwards-compatible feature.
+* a Z (patch) release indicates minimum set of bugfixes. Changing Z means a backwards-compatible change that doesn't add functionality.
+
+## Branches
+
+The AWS Load Balancer Operator repository contains two types of branches: the `main` branch and `release-X.Y` branches.
+
+The main branch is where development happens. All the latest code, including breaking changes, happens on `main`.
+The `release-X.Y` branches contain stable, backwards compatible code. Every minor (`X.Y`) release, a new such branch is created.
+
+## Channels
+
+The AWS Load Balancer Operator's releases get published in two types of [OLM channels](https://olm.operatorframework.io/docs/glossary/#channel): the minor `release-vX.Y` and the major `release-vX`.
+
+The minor channels contain patch releases. The major channels contain all patch releases from all minor channels.
+
+## OpenShift Version Compatibility
+
+The table below illustrates the OpenShift versions for which various AWS Load Balancer Operator releases were intended:
+
+| OCP version | AWS Load Balancer Operator branch  | AWS Load Balancer Operator OLM channel |
+| :---------: | :-------------------------------:  | :------------------------------------: |
+| 4.16        | release-1.1                        | stable-v1.1, stable-v1                 |
+| 4.15        | release-1.1                        | stable-v1.1, stable-v1                 |
+| 4.14        | release-1.1                        | stable-v1.1, stable-v1                 |
+| 4.13        | release-1.0                        | stable-v1.0, stable-v1                 |
+| 4.12        | release-0.2                        | stable-v0.2, stable-v0                 |
+| 4.11        | release-0.1                        | stable-v0.1, stable-v0                 |
+
+## Support model
+
+| AWS Load Balancer Operator release | Support model   |
+| :--------------------------------: | :-------------: |
+| 1.1                                | Full Support    |
+| 1.0                                | Full Support    |
+| 0.2                                | End of Life     |
+| 0.1                                | End of Life     |
+
+### Full support
+
+During the Full Support phase, qualified critical and important security fixes will be released as they become available.
+Urgent and high priority bug fixes will be released as they become available. Other fixes and qualified patches may be released via periodic updates.
+To receive security and bug fixes, users are expected to upgrade the operator to the most current supported patch version.
+Users should install operator releases on the designated OpenShift versions (see [OpenShift Version Compatibility](#openshift-version-compatibility)).