[PATCH] Documentation: security: mention long term stable release

We occasionally backport changes to v2026.04.0, so adapt the README.rst
and SECURITY.md accordingly.

Reported-by: Enrico Jörns <[email protected]>
Signed-off-by: Ahmad Fatoum <[email protected]>
---
 README.rst  |  5 +++++
 SECURITY.md | 10 ++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/README.rst b/README.rst
index 17bf288c4c60..71286904a866 100644
--- a/README.rst
+++ b/README.rst
@@ -273,6 +273,11 @@ are the release rules:
   We think that there is no need for pre releases, but if it's ever
   necessary, this is the scheme we follow.
 
+- Occasionally, a release may be designated a long term stable (LTS)
+  release and will continue to receive fixes for a longer period of
+  time. Refer to ``SECURITY.md`` in this directory to see, what
+  releases, besides the most recent, are actively maintained.
+
 - Only the monthly releases are archived on the web site. The tarballs
   are located in https://www.barebox.org/download/ and this location
   does never change, in order to make life easier for distribution
diff --git a/SECURITY.md b/SECURITY.md
index 9dd19d73d0aa..862dd14623d9 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -2,12 +2,18 @@
 
 ## Supported Versions
 
-The barebox project does not, at the moment, maintain any longer term
-support branches.
 Please update to new [barebox releases](https://github.com/barebox/barebox/releases)
 as they become available.
 Compatibility with old kernels is maintained over barebox releases.
 
+The [migration guides](https://www.barebox.org/doc/latest/migration-guides/index.html)
+can be helpful in adapting configuration to new releases.
+
+In addition, the barebox project currently maintains following long term stable (LTS)
+releases:
+
+  * [v2026.04.y](https://github.com/barebox/barebox/tree/stable/v2026.04)
+
 ## Reporting a Vulnerability
 
 Please report security vulnerabilities to [email protected].
-- 
2.47.3