Update readme (#323)

* docs: update README.md

README.md

@@ -1,14 +1,35 @@
+> [!WARNING]
+> The state of this repertory is changed to maintenance. We will not accept any more feature requests. Please check [Change of status](#change-of-status) for details
+
+
 # mbedtls
 
 [![Build Status](https://travis-ci.com/fortanix/rust-mbedtls.svg?branch=master)](https://travis-ci.com/fortanix/rust-mbedtls)
 
+
 This is an idiomatic Rust wrapper for MbedTLS, allowing you to use MbedTLS with
 only safe code while being able to use such great Rust features like error
 handling and closures.
 
 Additionally, building on MbedTLS's focus on embedded use, this crate can be
 used in a no_std environment.
 
+## Change of status
+
+We discovered that `mbedtls 3.X` is not thread safe and will not work properly with multiple threads.
+And the new PSA approach does not match our needs. So we now decided to stay on mbedtls `2.28.X`; and the state of this repertory is changed to maintenance. We will not accept any more feature requests.
+
+Related issue: [#320](https://github.com/fortanix/rust-mbedtls/issues/320)
+
+Reference links:
+
+- Design changes:
+  - https://lists.trustedfirmware.org/archives/list/[email protected]/message/RJ7YPNBNWUNW2ICQJ72H2JMKPDKGQOLT/
+- Bugs
+  - https://github.com/fortanix/rust-mbedtls/issues/301
+  - https://github.com/fortanix/rust-mbedtls/issues/293
+  - https://github.com/Mbed-TLS/mbedtls/issues/3263
+
 ## Building
 
 This crate depends on the mbedtls-sys-auto crate, see below for build details.