platform: arm64: thinkpad-t14s-ec: new driver

Introduce EC driver for the ThinkPad T14s Gen6 Snapdragon, which is in
theory compatible with ThinkPad ACPI. On Linux the system is booted with
device tree, which is not supported by the ThinkPad ACPI driver
(drivers/platform/x86/lenovo/thinkpad_acpi.c). Also most of the hardware
compatibility is handled via ACPI tables, which are obviously not used
when booting via device tree. Thus adding DT compatibility to the
existing driver is not worth it as there is almost no code sharing.

The driver currently exposes features, which are not available
via other means:

 * Extra Keys
 * System LEDs
 * Keyboard Backlight Control

The driver has been developed by reading the ACPI DSDT. There
are some more features around thermal control, which are not
yet supported by the driver.

The speaker mute and mic mute LEDs need some additional changes
in the ALSA UCM to be set automatically.

Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on Thinkpad T14S OLED
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Link: https://patch.msgid.link/20250918-thinkpad-t14s-ec-v5-2-ac0bc6382c5c@collabora.com
[ij: folded in patch from Chen Ni <nichen@iscas.ac.cn>]
Link: https://patch.msgid.link/20250926091302.817919-1-nichen@iscas.ac.cn
[ij: folded in patch from Lukas Bulwahn <lbulwahn@redhat.com>]
Link: https://patch.msgid.link/20250926071859.138396-1-lukas.bulwahn@redhat.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: sre

MAINTAINERS

@@ -25071,6 +25071,12 @@ W:	http://thinkwiki.org/wiki/Ibm-acpi
 T:	git git://repo.or.cz/linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git
 F:	drivers/platform/x86/lenovo/thinkpad_acpi.c
 
+THINKPAD T14S EMBEDDED CONTROLLER DRIVER
+M:	Sebastian Reichel <sre@kernel.org>
+S:	Maintained
+F:	Documentation/devicetree/bindings/embedded-controller/lenovo,thinkpad-t14s-ec.yaml
+F:	drivers/platform/arm64/lenovo-thinkpad-t14s.c
+
 THINKPAD LMI DRIVER
 M:	Mark Pearson <mpearson-lenovo@squebb.ca>
 L:	platform-driver-x86@vger.kernel.org

drivers/platform/arm64/Kconfig

@@ -70,4 +70,24 @@ config EC_LENOVO_YOGA_C630
 
 	  Say M or Y here to include this support.
 
+config EC_LENOVO_THINKPAD_T14S
+	tristate "Lenovo Thinkpad T14s Embedded Controller driver"
+	depends on ARCH_QCOM || COMPILE_TEST
+	depends on I2C
+	depends on INPUT
+	select INPUT_SPARSEKMAP
+	select LEDS_CLASS
+	select NEW_LEDS
+	select SND_CTL_LED if SND
+	help
+	  Driver for the Embedded Controller in the Qualcomm Snapdragon-based
+	  Lenovo Thinkpad T14s, which provides access to keyboard backlight
+	  and status LEDs.
+
+	  This driver provides support for the mentioned laptop where this
+	  information is not properly exposed via the standard Qualcomm
+	  devices.
+
+	  Say M or Y here to include this support.
+
 endif # ARM64_PLATFORM_DEVICES

drivers/platform/arm64/Makefile

@@ -8,3 +8,4 @@
 obj-$(CONFIG_EC_ACER_ASPIRE1)	+= acer-aspire1-ec.o
 obj-$(CONFIG_EC_HUAWEI_GAOKUN)	+= huawei-gaokun-ec.o
 obj-$(CONFIG_EC_LENOVO_YOGA_C630) += lenovo-yoga-c630.o
+obj-$(CONFIG_EC_LENOVO_THINKPAD_T14S) += lenovo-thinkpad-t14s.o