Add references

Co-authored-by: Peter Bierma <[email protected]>

Author: hroncok

Doc/c-api/object.rst

@@ -512,7 +512,7 @@ Object Protocol
 .. c:function:: PyObject* PyObject_SelfIter(PyObject *obj)
 
    This is equivalent to the Python ``__iter__(self): return self`` method.
-   It is intended for iterator types, to be used in the ``tp_iter`` slot.
+   It is intended for :term:`iterator` types, to be used in the :c:member:`PyTypeObject.tp_iter` slot.
 
 
 .. c:function:: PyObject* PyObject_GetAIter(PyObject *o)