[docs][PATCH V2 2/3] ref-manual/variables.rst: add UPSTREAM_STABLE_RELEASE_REGEX and STABLE_VERSION_PARTS

[Qi.Chen@windriver.com]

From: Chen Qi <Qi.Chen@windriver.com>

Document the two new variables used for stable point release upgrades:
- UPSTREAM_STABLE_RELEASE_REGEX: filter regex for upstream version checks
- STABLE_VERSION_PARTS: controls how many version parts form the stable prefix

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
---
 documentation/ref-manual/variables.rst | 28 ++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
index fe3d5a999..cb11f7901 100644
--- a/documentation/ref-manual/variables.rst
+++ b/documentation/ref-manual/variables.rst
@@ -10097,6 +10097,15 @@ system and gives an overview of their function and contents.
 
          SSTATE_SKIP_CREATION = "1"
 
+   :term:`STABLE_VERSION_PARTS`
+      The number of leading dot-separated components of :term:`PV` that
+      constitute the stable version prefix. Used by the
+      :ref:`ref-classes-upstream-stable-release-point` class to generate
+      :term:`UPSTREAM_STABLE_RELEASE_REGEX`. Defaults to ``"2"``.
+
+      For example, with ``PV = "259.5"`` and ``STABLE_VERSION_PARTS = "1"``,
+      the generated regex matches versions starting with ``259``.
+
    :term:`STAGING_BASE_LIBDIR_NATIVE`
       Specifies the path to the ``/lib`` subdirectory of the sysroot
       directory for the build host.
@@ -12001,6 +12010,25 @@ system and gives an overview of their function and contents.
 
          UPSTREAM_VERSION_UNKNOWN = "1"
 
+   :term:`UPSTREAM_STABLE_RELEASE_REGEX`
+      A regular expression used to filter upstream versions during version
+      checks so that only versions within the same stable series are
+      considered. When set, BitBake's fetchers (git, wget, crate) apply this
+      regex to discovered upstream versions and discard any that do not match.
+
+      For example, if a recipe is at version ``1.4.2`` and the regex is
+      ``^1\.4(\.\d+)*$``, then ``1.4.7`` would be a valid upgrade candidate
+      but ``1.5.0`` would not.
+
+      For recipes with dot-separated versions, inherit the
+      :ref:`ref-classes-upstream-stable-release-point` class to generate this
+      variable automatically. For other versioning schemes, set it directly::
+
+         UPSTREAM_STABLE_RELEASE_REGEX = "^10\.2p\d+$"
+
+      See :ref:`ref-manual/release-process:stable point release upgrades` for
+      the criteria under which this variable should be set.
+
    :term:`USE_DEVFS`
       Determines if ``devtmpfs`` is used for ``/dev`` population. The
       default value used for :term:`USE_DEVFS` is "1" when no value is
-- 
2.54.0