open door

open door is a Noun

Definition:

[1] Open or free admission to all; hospitable welcome; free opportunity.

[2] In modern diplomacy, opportunity for political and commercial intercourse open to all upon equal terms, esp. with reference to a nation whose policy is wholly or partially fixed by nations foreign to itself, or to territory newly acquired by a conquering nation. In this sense, often used adjectively, as, open-door system, open-door policy, etc.