[doc] HLD: Static analysis CI gates for SONiC repositories

doc/security/README.md

@@ -0,0 +1,28 @@
+# SONiC Security
+
+This directory is the home for SONiC security-related design documents and initiatives.
+
+## Documents in this directory
+
+| Document | Description |
+|----------|-------------|
+| [Static Analysis CI Gates](static-analysis-ci-hld.md) | Fleet-wide static analysis (Python, C/C++, Rust, Go, shell) wired into the existing per-repository build pipelines as a merge gate, driven from a shared `sonic-net/sonic-ci` repository. |
+
+## Related documents elsewhere in `doc/`
+
+Predating this directory, several security-related HLDs live in their own feature
+directories. They are listed here for discoverability; they have not been moved, because
+existing links and references point at their current locations.
+
+| Document | Location |
+|----------|----------|
+| Container Hardening | [`doc/Container Hardening/SONiC_container_hardening_HLD.md`](../Container%20Hardening/SONiC_container_hardening_HLD.md) |
+| Password Hardening | [`doc/passw_hardening/hld_password_hardening.md`](../passw_hardening/hld_password_hardening.md) |
+| Secure Boot | [`doc/secure_boot/hld_secure_boot.md`](../secure_boot/hld_secure_boot.md) |
+| Secure Upgrade | [`doc/secure_upgrade/secure_upgrade.md`](../secure_upgrade/secure_upgrade.md) |
+
+## Adding a document
+
+New security-related design documents should be added to this directory and registered in
+the table above. Follow the standard SONiC HLD template at
+[`doc/guidelines/hld_template.md`](../guidelines/hld_template.md).