Ask HN: How to manage developer relations across embedded specialist teams?

The company I work for has offices around the world, and most of those host fairly isolated teams that don't really need to collaborate or communicate daily.

However, I'm part of a specialist (mobile) team, and we strive to maintain close contact with other mobile teams embedded in other parts of the company.

Specifically, we want to promote healthy developer relations, where the "wider" mobile team is aware of all architectural decisions made on different mobile projects, all members actively review each other's code, maintain shared libraries, etc.

While standard distributed team management challenges apply here (timezones, Slack etiquette, not knowing people "in person"), I'm interested in how to manage this on a more personal level. What are the key components of creating solidarity across all specialist developers, when they may work on different projects and thus "belong" to different local teams?