Added more information on mux and wire_switch for segments in the arch file

Clarified these are defaults only for rr-graph construction.

Author: vaughnbetz

doc/src/arch/reference.rst

@@ -2026,15 +2026,15 @@ The ``<segment>`` tag and its contents are described below.
 
 .. arch:tag:: <mux name="string"/>
 
-    :req_param name: Name of the mux switch type used to drive this type of segment.
+    :req_param name: Name of the mux switch type used to drive this type of segment by default, from both block outputs and other wires. This information is used during rr-graph construction, and a custom switch block can override this switch type for specific connections if desired.
 
     .. note:: For UNIDIRECTIONAL only.
 
     Tag must be included and ``name`` must be the same as the name you give in ``<switch type="mux" name="...``
 
 .. arch:tag:: <wire_switch name="string"/>
 
-    :req_param name: Name of the switch type used by other wires to drive this type of segment.
+    :req_param name: Name of the switch type used by other wires to drive this type of segment by default. This information is used during rr-graph construction, and a custom switch block can override this switch type for specific connections if desired.
 
     .. note:: For BIDIRECTIONAL only.