I have found the solution if someone also has a similar issue. The logic by which frappe.set_route object argument is transformed into filters described in frappe/public/js/frappe/list/list_view.js in function ListView::parse_filters_from_route_options . For my particular case, it should be written this way:
frappe.set_route('List', 'Sales Order', 'List', {'<Child Table Doctype(Sales Order Item)>.item_code':my_specific_item_code});