This protocol allows the error level mask for DEBUG() macros to be adjusted for DXE Phase modules
Include/Guid/DebugMask.h

PROTOCOL Information

PROTOCOL's Guid Name	PROTOCOL's Guid
gEfiDebugMaskProtocolGuid	{ 0x4c8a2451, 0xc207, 0x405b, {0x96, 0x94, 0x99, 0xea, 0x13, 0x25, 0x13, 0x41} }

Refer to Header File