It's called nominative use, and describing a thing as "HDMI compatible" is permitted.
One doesn't get to use the logo or even the typeface, but that's not a dealbreaker at all for the purposes being discussed here. Words themselves are OK (and initialisms, such as "HDMI," are just a subset of words like nouns and verbs are).
One doesn't get to use the logo or even the typeface, but that's not a dealbreaker at all for the purposes being discussed here. Words themselves are OK (and initialisms, such as "HDMI," are just a subset of words like nouns and verbs are).
The wiki has some background: https://en.wikipedia.org/wiki/Nominative_use