drivers: firmware: TISCI driver support

Added TISCI driver for supported devices using the binding ti,k2g-sci.
This is used to communicate via the secury proxy channel for clock,
resource and power domain management.
Refer: https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/general/TISCI_header.html

Signed-off-by: Dave Joseph <d-joseph@ti.com>

drivers/firmware/CMakeLists.txt

@@ -3,4 +3,5 @@
 # zephyr-keep-sorted-start
 add_subdirectory_ifdef(CONFIG_ARM_SCMI scmi)
 add_subdirectory_ifdef(CONFIG_NRF_IRONSIDE nrf_ironside)
+add_subdirectory_ifdef(CONFIG_TISCI tisci)
 # zephyr-keep-sorted-stop

drivers/firmware/Kconfig

@@ -13,6 +13,7 @@ config ARM_SCMI
 # zephyr-keep-sorted-start
 source "drivers/firmware/nrf_ironside/Kconfig"
 source "drivers/firmware/scmi/Kconfig"
+source "drivers/firmware/tisci/Kconfig"
 # zephyr-keep-sorted-stop
 
 endmenu

drivers/firmware/tisci/CMakeLists.txt

@@ -0,0 +1,6 @@
+# Copyright (c) 2025, Texas Instruments
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_library()
+
+zephyr_library_sources_ifdef(CONFIG_TISCI tisci.c)

drivers/firmware/tisci/Kconfig

@@ -0,0 +1,22 @@
+# Copyright (c) 2025, Texas Instruments
+# SPDX-License-Identifier: Apache-2.0
+
+config TISCI
+	bool "TISCI Firmware driver"
+	default y
+	depends on DT_HAS_TI_K2G_SCI_ENABLED
+	select MBOX
+	help
+	  TISCI firmware driver is a frontend interface
+	  to TI System Controller interface firmware through
+	  secureproxy mailbox.
+
+if TISCI
+
+config TISCI_INIT_PRIORITY
+	int "TISCI init priority"
+	default KERNEL_INIT_PRIORITY_OBJECTS
+	help
+	  Init priority for the TISCI driver.
+
+endif

dts/bindings/firmware/ti,k2g-sci.yaml

@@ -0,0 +1,25 @@
+# Copyright 2025 Texas Instruments Incorporated.
+# SPDX-License-Identifier: Apache-2.0
+
+description: TISCI Client Driver
+
+compatible: "ti,k2g-sci"
+
+include: [base.yaml]
+
+properties:
+  reg:
+    required: true
+
+  ti,host-id:
+    type: int
+    required: true
+    description: Host ID for processor
+
+  mboxes:
+    description: phandle to the MBOX controller (TX and RX are required)
+    required: true
+
+  mbox-names:
+    description: MBOX channel names (must be called "tx" and "rx")
+    required: true