drivers: Add hardware timestamp engine (HTE) subsystem

Some devices can timestamp system lines/signals/Buses in real-time
using the hardware counter or other hardware means which can give
finer granularity and help avoid jitter introduced by software
timestamping. To utilize such functionality, this patchset creates
HTE subsystem where devices can register themselves as providers so
that the consumers devices can request specific line from the
providers. The patch also adds compilation support in Makefile and
menu options in Kconfig.

The provider does following:
- Registers chip with the framework.
- Provides translation hook to convert logical line id.
- Provides enable/disable, request/release callbacks.
- Pushes timestamp data to HTE subsystem.

The consumer does following:
- Initializes line attribute.
- Gets HTE timestamp descriptor.
- Requests timestamp functionality.
- Puts HTE timestamp descriptor.

Signed-off-by: Dipen Patel <dipenp@nvidia.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/Kconfig

@@ -239,4 +239,6 @@ source "drivers/most/Kconfig"
 
 source "drivers/peci/Kconfig"
 
+source "drivers/hte/Kconfig"
+
 endmenu

drivers/Makefile

@@ -188,3 +188,4 @@ obj-$(CONFIG_INTERCONNECT)	+= interconnect/
 obj-$(CONFIG_COUNTER)		+= counter/
 obj-$(CONFIG_MOST)		+= most/
 obj-$(CONFIG_PECI)		+= peci/
+obj-$(CONFIG_HTE)		+= hte/

drivers/hte/Kconfig

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menuconfig HTE
+	bool "Hardware Timestamping Engine (HTE) Support"
+	help
+	  Hardware Timestamping Engine (HTE) Support.
+
+	  Some devices provide a hardware timestamping engine which can
+	  timestamp certain device lines/signals in realtime. It comes with a
+	  benefit for the applications needing accurate timestamping event with
+	  less jitter. This framework provides a generic interface to such HTE
+	  providers and consumer devices.
+
+	  If unsure, say no.
+

drivers/hte/Makefile

@@ -0,0 +1,2 @@
+obj-$(CONFIG_HTE)		+= hte.o
+