portmanteau word vs coinage

portmanteau word and coinage both are nouns.

Word	Noun	Adjective	Verb	Adverb
portmanteau word	Yes	No	No	No
coinage	Yes	No	No	No

As nouns, coinage is a hypernym of portmanteau word; that is, coinage is a word with a broader meaning than portmanteau word:

portmanteau word: a new word formed by joining two others and combining their meanings
coinage: a newly invented word or phrase

Other hypernyms of portmanteau word include neologism, neology.

portmanteau word (noun)	coinage (noun)
a new word formed by joining two others and combining their meanings	the act of inventing a word or phrase
	a newly invented word or phrase
	coins collectively