docs: Add version support description
@@ -120,7 +120,22 @@ MVP definition
the three first ones in the list above are mandatory (see section 9.1 of the
specification).
-- Supported versions: only TLS 1.3, version negotiation is not supported.
+- Supported versions:
+
+ - only TLS 1.3, version negotiation is not supported.
+
+ - TLS 1.3 and 1.2 can be disable/enable with build option. One of them MUST be
+ enabled. Supported build options:
+
+ | MBEDTLS_SSL_PROTO_TLS1_2 | MBEDTLS_SSL_PROTO_TLS1_3 |
+ | ------------------------ | ------------------------ |
+ | yes | no |
+ | no | yes |
+ | yes | yes |
+
+ - If both TLS 1.3 and TLS 1.2 are enabled, only one of them can be configured
+ enabled via `mbedtls_ssl_conf_{min,max}_version`. Otherwise, `mbedtls_ssl_setup`
+ will raise `MBEDTLS_ERR_SSL_BAD_CONFIG` error.
- Compatibility with existing SSL/TLS build options:
