Update other node fields after IEF submit.

Hi, I have one problem which I can't figured it out how to do it. I have node form with inline entity form. What I would like to do is to update another field on a node, when you add/remove/update node inside inline entity form.
Example: On Article node I have two fields, field_page_reference (reference to Page content type), field_some_textfield (normal textfield price). On Manage form display for field_page_reference I set inline_entity_form widget. Now when user adds a node on field_page_reference, I would like to update value of field_some_textfield. How can i do that?

I looked all hooks in inline_entity_form.api.php file, but don't know exactly how can I achieve that.