doc: TPMI: Add debugfs documentation

Describe fields in the TPMI debugfs folder.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230712225950.171326-4-srinivas.pandruvada@linux.intel.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

Documentation/ABI/testing/debugfs-tpmi

+What:		/sys/kernel/debug/tpmi-<n>/pfs_dump
+Date:		November 2023
+KernelVersion:	6.6
+Contact:	srinivas.pandruvada@linux.intel.com
+Description:
+The PFS (PM Feature Structure) table, shows details of each power
+management feature. This includes:
+tpmi_id, number of entries, entry size, offset, vsec offset, lock status
+and disabled status.
+Users:		Debugging, any user space test suite
+
+What:		/sys/kernel/debug/tpmi-<n>/tpmi-id-<n>/mem_dump
+Date:		November 2023
+KernelVersion:	6.6
+Contact:	srinivas.pandruvada@linux.intel.com
+Description:
+Shows the memory dump of the MMIO region for a TPMI ID.
+Users:		Debugging, any user space test suite
+
+What:		/sys/kernel/debug/tpmi-<n>/tpmi-id-<n>/mem_write
+Date:		November 2023
+KernelVersion:	6.6
+Contact:	srinivas.pandruvada@linux.intel.com
+Description:
+Allows to write at any offset. It doesn't check for Read/Write access
+as hardware will not allow to write at read-only memory. This write is
+at offset multiples of 4. The format is instance,offset,contents.
+Example:
+echo 0,0x20,0xff > mem_write
+echo 1,64,64 > mem_write
+Users:		Debugging, any user space test suite

MAINTAINERS

@@ -10732,6 +10732,7 @@ INTEL TPMI DRIVER
 M:	Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
 L:	platform-driver-x86@vger.kernel.org
 S:	Maintained
+F:	Documentation/ABI/testing/debugfs-tpmi
 F:	drivers/platform/x86/intel/tpmi.c
 F:	include/linux/intel_tpmi.h