Add terminology section, short so far.

Hardware-API.md

@@ -9,6 +9,11 @@ The API should be Pythonic, obvious and relatively minimal.  There should be a c
 
 The existing pyb module already provides such abstraction but it is not as clean or consistent or general as it could be.  The new hardware API will co-exist alongside the pyb module (only for stmhal port, eg pyboard) so that existing scripts still run.  The pyb module will eventually be deprecated, but only after all functionality finds another home (which may be some time).
 
+# Terminology
+
+* Port - when used in this document, refers to some kind of hardware port.
+* Software - MicroPython ported to a particular CPU/MCU/SoC. A separate word used to disambiguate word "port" (which otherwise may refer to a hardware or software port)
+
 # Use cases
 
 Create a UART with various pin configurations: