platform:x86: add Intel P-Unit mailbox IPC driver

This driver provides support for P-Unit mailbox IPC on Intel platforms.
The heart of the P-Unit is the Foxton microcontroller and its firmware,
which provide mailbox interface for power management usage.

Signed-off-by: Qipeng Zha <qipeng.zha@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index e9caa4b..2739161 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5680,12 +5680,14 @@
 F:	drivers/dma/mic_x100_dma.h
 F	Documentation/mic/
 
-INTEL PMC IPC DRIVER
+INTEL PMC/P-Unit IPC DRIVER
 M:	Zha Qipeng<qipeng.zha@intel.com>
 L:	platform-driver-x86@vger.kernel.org
 S:	Maintained
 F:	drivers/platform/x86/intel_pmc_ipc.c
+F:	drivers/platform/x86/intel_punit_ipc.c
 F:	arch/x86/include/asm/intel_pmc_ipc.h
+F:	arch/x86/include/asm/intel_punit_ipc.h
 
 IOC3 ETHERNET DRIVER
 M:	Ralf Baechle <ralf@linux-mips.org>