Please describe the requirements of DXE Dispatcher.
1. Support fixed execution order of DXE drivers. 
2. Determine DXE driver execution order based on each driver’s dependencies.
3. Support “emergency patch” DXE drivers.
4. Support platform specific security policies for DXE driver execution.
Below is an instruction that describes a task. Write a response that appropriately completes the request. ### Instruction: Please describe the requirements of DXE Dispatcher. ### Response: 1. Support fixed execution order of DXE drivers. 
2. Determine DXE driver execution order based on each driver’s dependencies.
3. Support “emergency patch” DXE drivers.
4. Support platform specific security policies for DXE driver execution. 