I second the "need to know" basis.
If there's a difficulty that's causing confusion or problems with someone, explain a little about it to that person.
If there isn't, no need to tell anyone.
Recently, in having a discussion about a local issue, with someone I don't particularly like (head of a local group who makes some bad decisions, in my view) it became necessary for me to say something -- but I didn't want to disclose to this person. I instead compromised by mentioning that I am of an introvert personality. That's as far as I was willing to go in this particular instance, with this specific person, and all that needed to be said regarding the difficulty.
Tony Attwood has recommended a similar method -- instead of disclosing the autism outright, disclose a trait or symptom, for example if noise sensitivity is preventing you from attending the parties of a friend who throws loud, lively ones and you don't know how to explain why you keep making excuses, you can say something like: "I'm sorry I keep turning down your parties, please don't take it personally. I'm afraid I experience a thing called misophonia where loud places and lots of noise overwhelms me."