LANGUAGE SUBTAG REGISTRATION FORM: pinyin

[CE Whitehead]

Hi, I do not know where to go on the argument as to whether written Chinese is Mandarin or not.  All I have is the Wikipedia article and such to go on (see http://en.wikipedia.org/wiki/Chinese_writing_system), which makes some sense to me.
 
Does anyone have any other references on this to suggest?  Or does the Wikipedia article cover everything here?