update os scheduling policy docs

Author: picnixz

Doc/library/os.rst

@@ -5411,6 +5411,8 @@ information, consult your Unix manpages.
 The following scheduling policies are exposed if they are supported by the
 operating system.
 
+.. _os-scheduling-policy:
+
 .. data:: SCHED_OTHER
 
    The default scheduling policy.
@@ -5516,6 +5518,8 @@ operating system.
 
    Voluntarily relinquish the CPU.
 
+   See also :manpage:`sched_yield(2)`.
+
 
 .. function:: sched_setaffinity(pid, mask, /)