The key to handling jointly developed IP is allocating the benefit obtained from IP properly in view of ownership and control allocation. People often confuse three concepts: benefits, ownership, and control. In fact, these three are not the same thing.
The jointly developed IP can be handled by separating the three. For example, the ownership can be allocated to one party, but the benefits can be shared regardless of ownership.
In another example, the ownership can be allocated to one party, but the other party can retain or share control and benefit from it by signing athrough contract by entering into an IP agreement.. Having an agreement also provides an option to handle jointly developed IP consistently in a global scheme.
These two examples illustrate potential ways to handle a jointly developed IP. Of course, the best solution would be to consult a lawyer for your specific situation.