doc: update backport guidelines

Updating the docs to elaborate on the stable release
characteristics and better document the current practice
about new features in stable releases.

Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
Acked-by: Luca Boccassi <bluca@debian.org>
Acked-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>

diff --git a/doc/guides/contributing/stable.rst b/doc/guides/contributing/stable.rst
index 20b0816..69d8312 100644 (file)
--- a/doc/guides/contributing/stable.rst
+++ b/doc/guides/contributing/stable.rst
@@ -18,6 +18,10 @@ backported fixes over an extended period of time. This provides downstream
 consumers of DPDK with a stable target on which to base applications or
 packages.
 
+The primary characteristics of stable releases is that they attempt to
+fix issues and not introduce any new regressions while keeping backwards
+compatibility with the initial release of the stable version.
+
 The Long Term Support release (LTS) is a designation applied to a Stable
 Release to indicate longer term support.
 
@@ -93,14 +97,32 @@ commit message body as follows::
 
 Fixes not suitable for backport should not include the ``Cc: stable@dpdk.org`` tag.
 
-Features should not be backported to stable releases. It may be acceptable, in
-limited cases, to back port features for the LTS release where:
-
-* There is a justifiable use case (for example a new PMD).
-* The change is non-invasive.
-* The work of preparing the backport is done by the proposer.
-* There is support within the community.
-
+To support the goal of stability and not introducing regressions,
+new code being introduced is limited to bug fixes.
+New features should not be backported to stable releases.
+
+In some limited cases, it may be acceptable to backport a new feature
+to a stable release. Some of the factors which impact the decision by
+stable maintainers are as follows:
+
+* Does the feature break API/ABI?
+* Does the feature break backwards compatibility?
+* Is it for the latest LTS release (to avoid LTS upgrade issues)?
+* Is there a commitment from the proposer or affiliation to validate the feature
+  and check for regressions in related functionality?
+* Is there a track record of the proposer or affiliation validating stable releases?
+* Is it obvious that the feature will not impact existing functionality?
+* How intrusive is the code change?
+* What is the scope of the code change?
+* Does it impact common components or vendor specific?
+* Is there a justifiable use case (a clear user need)?
+* Is there a community consensus about the backport?
+
+Performance improvements are generally not considered to be fixes,
+but may be considered in some cases where:
+
+* It is fixing a performance regression that occurred previously.
+* An existing feature in LTS is not usable as intended without it.
 
 The Stable Mailing List
 -----------------------