Add factory-reset-toggle pin name

factory-reset-toggle indicates the state of the pin that determines
whether a factory reset has been requested. The toggle switch could
be high or low; if it is in a different state than what was recorded
before, then a factory reset is requested.

Signed-off-by: Isaac Kurth <isaac.kurth@ibm.com>
Change-Id: I09e97489cff8114068d542a3ba77cecd13aefc81
diff --git a/designs/device-tree-gpio-naming.md b/designs/device-tree-gpio-naming.md
index 2b9d46c..98ddb03 100644
--- a/designs/device-tree-gpio-naming.md
+++ b/designs/device-tree-gpio-naming.md
@@ -86,7 +86,13 @@
 These are special case and/or grandfathered in pin names.
 
 Defined:
-- air-water (indicates whether system is air or water cooled)
+#### air-water
+Indicates whether system is air or water cooled
+
+#### factory-reset-toggle
+The software records the state of this GPIO and checks upon reboot if the state
+has changed since the last reboot. If it has, it indicates that a factory reset
+should be performed.
 
 ### POWER Specific GPIO's
 Below are GPIO names specific to the POWER processor based servers.