Like classes and controllers, protocols itself can also be extended and can be used to produce new protocols.

Here we are creating a base Protocol with superset methods.
We can also call it original protocol. it is inherited from NSObject, like other classes in C.

@protocol BaseProtocolDelegate <NSObject>
- (void)testProtocol;
@end
@interface BaseViewController : UIViewController

Here we are creating a child Protocol inheriting Base protocol

@protocol ChildProtocol <BaseProtocolDelegate>
- (void)testChildProtocol;
@end
@interface FirstViewController : BaseViewController
@property (nonatomic, retain)id <ChildProtocol> childProtocol;

we can call/use methods of protocols like:

[childProtocol testProtocol];