Help with one to many data structure

I just started to evaluate Yjs so I apologise for my noob question.
I am currently using react + y-websocket + immer-yjs and I have a dummy model with a one to many relation eg:

Item {
   id: string
   title: string
   subItems: SubItem[]
}

SubItem {
  id: string
  itemId: string
  title: string
}

Ideally I would like to persist this data into a remote Db. Can you please suggest me a possible data structure and or some tips on how to approach this?

Thank you so much!

@integra Item and SubItem would be Y.Map types and subItems a Y.Array. Fairly straightforward unless I am missing something.