Hi Alvin23,
Welcome to citehr.com!!
Resolving Conflict of Interest between two departments is usually done by the CEO keeping in mind the goals of the company.
Tools/methods used by CEO with whom i have worked closely:-
1. Meetings both sides - hear their viewpoints on respective issue.
2. Reverse the roles - both the sides present the other's perspectives.
3. Ask them to meet among themselves to arrive at the situation - which usually happens.
4. If step 3 fails - the CEO took the call on the matter.
Hope this has answered your question.
Cheerio
Rajat Joshi