improve availability wording

Author: picnixz

Doc/library/intro.rst

@@ -65,11 +65,8 @@ Notes on availability
   *Availability: Linux >= 3.17 with glibc >= 2.27* requires both Linux 3.17 or
   newer and glibc 2.27 or newer.
 
-* "Availability" notes may also be used to indicate requirements on how Python
-  was built. For instance, "Availability: OpenSSL >= 3.5" note means that the
-  feature is available if Python has been built with OpenSSL 3.5 or later,
-  while "Availability: not AWS-LC" note means that the feature is not available
-  if Python has been built with AWS-LC instead of OpenSSL.
+* A particular library dependency with an optional minimal ``major.minor``
+  version constraint is indicated by *Availability: library >= major.minor*.
 
 
 .. _wasm-availability:

Doc/library/ssl.rst

@@ -28,7 +28,15 @@ probably additional platforms, as long as OpenSSL is installed on that platform.
    cause variations in behavior. For example, TLSv1.3 comes with OpenSSL version
    1.1.1.
 
+.. note::
+
+   Support for other implementations of ``libssl`` such as AWS-LC, BoringSSL,
+   or LibreSSL, may be assumed but not guaranteed. When a feature is known to
+   be unavailable for a sepcific backend, it will be explicitly mentioned in
+   an :ref:`Availability <availability>` note as *Availability: not <backend>*.
+
 .. warning::
+
    Don't use this module without reading the :ref:`ssl-security`.  Doing so
    may lead to a false sense of security, as the default settings of the
    ssl module are not necessarily appropriate for your application.