Some languages have an accepted transliteration to Latin characters, such as Hindi, Russian or Japanese. For example, the Hindi for 'The man is eating' written in Devanagari script is 'आदमी खा रहा है।'. Transliterated, it would be 'Aadmi kha raha hai.' (or something similar; this approach is often used online, especially if people don't have access to a Hindi keyboard.)
In this case, we're using the Latin script but still writing Hindi, so it would be acceptable to mark up either variation using the lang attribute:
<span lang="hi">आदमी खा रहा है।</span> or <span lang="hi">Aadmi kha raha hai.</span>
My question then is about languages that are normally written in the Latin alphabet themselves, but might have phonetic guides for non-speakers/learners — either IPA or ad hoc pronunciation — is there any best practice in terms of giving it semantic meaning?
For example, in Irish if I were to say "The man is eating", I would say "Tá an fear ag ithe." I can mark this up as:
<span lang="ga">Tá an fear ag ithe.</span>
If I were to give a pronunciation guide for non-speakers, I might say "Taw on far eg ih-he". The sentence isn't meaningless, (like 'lorem ipsum' text) but neither is the sentence in either English or Irish.
What is the correct use of language related attributes in HTML in this case, or is this use case just not covered currently by the specification?