Note that ISO 639-3 'hye' is an equivalent of 639-1 'hy', we use 639-1 codes if they exist.

Please also note that for UI translation only one locale per language is necessary, you probably would not translate to three different 'hy-...' languages, but only one 'hy'.

Or do you plan to submit locale data for the different locales as well? Locales and locale data are independent of UI translations, see https://wiki.documentfoundation.org/LibreOffice_Localization_Guide/How_To_Submit_New_Locale_Data

My suggestion would be to add

hy-AM  "Armenian, Eastern"
hyw-AM "Armenian, Western"

for UI translations.

'xcl' Classical Armenian is a historical liturgical language, see
http://www-01.sil.org/iso639-3/documentation.asp?id=xcl
It might make sense to add that to the language listbox only for document content, but note that you can easily mark document content with any language tag using the Language ComboBox edit field and enter xcl for this example.

Thank you for quick response. Indeed, ISO-639-1:hy = ISO-639-3:hye, and it is currently used in Republic of Armenia. However this causes ambiguity for building UI/localizations and specifically spell-checkers, due to differences between the USSR/RA orthography and rest of Eastern-Armenians (e.g. Iranian diaspora) which uses Classical Orthography with the rest of the languages. For xcl - yes it's historical and yes, we are committing complete UI translation in addition to support for documents.

Below are more details, to save research time for those who need it: 

Armenian language family has 4 official (state/literature) language standards, one of which uses additional orthography (Soviet/1940 or aka "modern"), as listed below:

A. Classical Orthography:

1) Classical Armenian (ISO-639-3:xcl)
2) Middle Armenian (ISO-639-3:axm)
3) Modern Western Armenian (ISO-639-3:hyw)
4) Modern Eastern Armenian (ISO-639-3:hye) used in Iranian diaspora

B. "Modern"/USSR1940 Armenian orthography:

5) Modern Eastern Armenian primarily used in RA and Russian diaspora

The Republic of Armenia doesn't fix a concrete language or orthography, so legally all 5 combinations are valid for official paperwork. 

For the document Language ComboBox/listbox we will need all 5 options.

For the translation, we are not planning to invest in (2) as there is not much academic research done in that direction. However we do plan to heavily invest in (1) as there are communities who actively work in this direction and even commercial companies who are willing to invest full localization. Therefore yes, we will implement the UI localization as well.

Since (4) and (5) are same the language (hy/hye) and differ only by orthography, we have to differentiate by the ISO-3166 Country code: e.g. use hy_RU/hye_RU for (5) and hy_IR/hye_IR for (4). 

For hy_AM/hye_AM the Institute of Language and Ministry of Education of RA have not yet made the official decision. There is an ongoing work on unified orthography, after completion of which, it will also be implemented under this code. For now we will use either IR or RU variant for this (subject to discussion with the min-edu). 

In the meantime, if you could kindly add all 5 locales, it would give us complete freedom of implementation, and in return we commit filling all 5 of those listed in the original request.

For the langauge ComboBox, please, also add Armenian

Eike Rathke committed a patch related to this issue.
It has been pushed to "master":

http://cgit.freedesktop.org/libreoffice/core/commit/?id=01d9d5b491d03004b3690c2a1ff4d99997e02a5a

Resolves: tdf#116058 add Armenian [hy-IR] [hy-RU] [hyw-AM] [xcl-AM]

It will be available in 6.1.0.

The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
http://wiki.documentfoundation.org/Testing_Daily_Builds

Affected users are encouraged to test the fix and report feedback.