Add s390x release note to v25.3.2 (#20479)

Author: jhlodin

src/current/_includes/releases/v25.3/v25.3.2.md

@@ -4,6 +4,10 @@ Release Date: September 22, 2025
 
 {% include releases/new-release-downloads-docker-image.md release=include.release %}
 
+<h3 id="v25-3-2-general-changes">General changes</h3>
+
+- Introduced support for running CockroachDB on s390x. Production binaries are delivered via IBM Passport Advantage.
+
 <h3 id="v25-3-2-sql-language-changes">SQL language changes</h3>
 
 - Added a new session variable, `disable_optimizer_rules`, which allows users to provide a comma-separated list of optimizer rules to disable during query optimization. This allows users to avoid rules that are known to create a suboptimal query plan for specific queries. [#152350][#152350]