bpo-45788: Link sys.prefix doc to 'Installation paths' (#29606)

... To the Installation paths section of the sysconfig doc.

Doc/library/sys.rst

@@ -1216,13 +1216,10 @@ always available.
 .. data:: prefix
 
    A string giving the site-specific directory prefix where the platform
-   independent Python files are installed; by default, this is the string
+   independent Python files are installed; on Unix, the default is
    ``'/usr/local'``.  This can be set at build time with the ``--prefix``
-   argument to the :program:`configure` script.  The main collection of Python
-   library modules is installed in the directory :file:`{prefix}/lib/python{X.Y}`
-   while the platform independent header files (all except :file:`pyconfig.h`) are
-   stored in :file:`{prefix}/include/python{X.Y}`, where *X.Y* is the version
-   number of Python, for example ``3.2``.
+   argument to the :program:`configure` script.  See
+   :ref:`installation_paths` for derived paths.
 
    .. note:: If a :ref:`virtual environment <venv-def>` is in effect, this
       value will be changed in ``site.py`` to point to the virtual

Doc/library/sysconfig.rst

@@ -60,6 +60,7 @@ Example of usage::
    >>> sysconfig.get_config_vars('AR', 'CXX')
    ['ar', 'g++']
 
+.. _installation_paths:
 
 Installation paths
 ------------------
@@ -72,7 +73,7 @@ Every new component that is installed using :mod:`distutils` or a
 Distutils-based system will follow the same scheme to copy its file in the right
 places.
 
-Python currently supports seven schemes:
+Python currently supports six schemes:
 
 - *posix_prefix*: scheme for POSIX platforms like Linux or macOS.  This is
   the default scheme used when Python or a component is installed.
@@ -84,6 +85,7 @@ Python currently supports seven schemes:
   located under the user home directory.
 - *nt*: scheme for NT platforms like Windows.
 - *nt_user*: scheme for NT platforms, when the *user* option is used.
+- *osx_framework_user*: scheme for macOS, when the *user* option is used.
 
 Each scheme is itself composed of a series of paths and each path has a unique
 identifier.  Python currently uses eight paths:

Misc/NEWS.d/next/Documentation/2021-11-18-00-07-40.bpo-45788.qibUoB.rst

@@ -0,0 +1 @@
+Link doc for sys.prefix to sysconfig doc on installation paths.