[meta-virtualization][PATCH v3 4/6] xen, xen-tools: Document the version update process in README

["Christopher Clark" <christopher.w.clark@gmail.com>]

Describes the versions of Xen to be included in meta-virtualization
and recipe maintenance in release branches.

Signed-off-by: Christopher Clark <christopher.w.clark@gmail.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
---
 recipes-extended/xen/README | 50 +++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/recipes-extended/xen/README b/recipes-extended/xen/README
index f286bb5..b9117f0 100644
--- a/recipes-extended/xen/README
+++ b/recipes-extended/xen/README
@@ -36,3 +36,53 @@ as XSAs (http://xenbits.xen.org/xsa/). The easiest way to include those is to
 drop patches in 'recipes-extened/xen/files' and create a bbappend adding those
 patches to SRC_URI and they will be applied. Alternatively, you can override
 the SRC_URI to a git repo you provide that contains the patches.
+
+recipe maintenance
+------------------
+
+# Xen version update
+
+The following rules shall be followed to define which versions of Xen have
+recipes in meta-virtualization:
+
+- Before a Yocto release meta-virtualization shall have recipes for:
+    - the latest stable major version of Xen, and
+
+    - the current version of the Xen master branch (known as the git recipes)
+
+    - In addition, there may also be recipes included for the previous stable
+      major version of Xen, in the case where the latest stable major version
+      is new and the prior stable major version of Xen is to be the preferred
+      version for the Yocto release
+
+- On Yocto LTS and the latest stable Yocto release branch, the preferred Xen
+  major version that is present when the Yocto release is issued must stay
+  supported and the recipes shall be regularly updated to follow updates
+  available in the Xen stable branch for that Xen major release.
+
+- On Yocto LTS and the latest stable Yocto release branch, the recipes for the
+  latest Xen major version shall also be regularly updated to follow updates
+  available in the Xen stable branch for that Xen major release.
+
+- On the master / in-development Yocto branch, new Xen recipes shall be added
+  when there is a new Xen major release.
+
+    - depending on the timing of the next Yocto release, the new recipes may
+      be preferred, or the prior major version recipes may remain preferred
+      until after the Yocto release
+
+    - the recipes for the previous Xen stable major version shall be removed
+      from the branch when it is no longer the preferred Xen version
+
+- On Yocto LTS and the latest stable Yocto release branch, new Xen recipes
+  shall be added when there is a new Xen major release.
+
+    - The preferred version of the Xen recipes shall always stay at the same
+      Xen major version once a Yocto release has been issued, and shall receive
+      regular updates to track the stable Xen branch of that Xen release.
+
+    - When new Xen recipes are added to a Yocto branch for a new Xen major
+      version, then any older Xen recipes present, except for the original
+      preferred version recipes, shall be marked as not updated anymore by
+      adding a comment inside the recipes. The older recipes will not receive
+      any build tests or be updated to follow the Xen branch.
-- 
2.25.1