portmanteau vs neologism

portmanteau and neologism both are nouns.

Word	Noun	Adjective	Verb	Adverb
portmanteau	Yes	No	No	No
neologism	Yes	No	No	No

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

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

Other hypernyms of portmanteau include coinage, neology.

portmanteau (noun)	neologism (noun)
a large travelling bag made of stiff leather	the act of inventing a word or phrase
a new word formed by joining two others and combining their meanings	a newly invented word or phrase