Use an XPath query to set a root node on the tree, either based on a search from the root of the content tree, or by using a context-aware placeholder.
A placeholder finds the nearest published ID and runs its query from there, so for instance:
$parent/newsArticle
Will try to get the parent if available, but will then fall back to the nearest ancestor and query for all news article children there.
Available placeholders:
$current
: Current page or closest found ancestor
$parent
: Parent page or closest found ancestor
$root
: Root of the content tree
$site
: Ancestor node at level 1
Note: The placeholder can only be used at the beginning of the query.