add missing E1000_NAPI Configure.help text

@@ -12164,6 +12164,20 @@
   module, say M here and read <file:Documentation/modules.txt> as well
   as <file:Documentation/networking/net-modules.txt>.
 
+CONFIG_E1000_NAPI
+  NAPI is a new driver API designed to reduce CPU and interrupt load
+  when the driver is receiving lots of packets from the card. It is
+  still somewhat experimental and thus not yet enabled by default.
+
+  If your estimated Rx load is 10kpps or more, or if the card will be
+  deployed on potentially unfriendly networks (e.g. in a firewall),
+  then say Y here.
+
+  See <file:Documentation/networking/NAPI_HOWTO.txt> for more
+  information.
+
+  If in doubt, say N.
+
 AMD LANCE and PCnet (AT1500 and NE2100) support
 CONFIG_LANCE
   If you have a network (Ethernet) card of this type, say Y and read