Add support for the XIAO STM32C5 as Bridle Board Extension

CODEOWNERS

@@ -61,6 +61,7 @@
 /boards/seeed/xiao_rp2040/                @rexut
 /boards/seeed/xiao_rp2350/                @rexut
 /boards/seeed/xiao_samd21/                @rexut
+/boards/seeed/xiao_stm32c5/               @rexut
 /boards/shields/                          @rexut
 /boards/shields/can_timing_adj/           @rexut
 /boards/shields/grove/                    @rexut

boards/seeed/xiao_stm32c5/Kconfig.defconfig

@@ -0,0 +1,57 @@
+# Seeed Studio XIAO STM32C5 board extended configuration
+
+# SPDX-FileCopyrightText: Copyright (c) 2026 TiaC Systems
+# SPDX-License-Identifier: Apache-2.0
+
+# Workaround for not being able to have commas in macro arguments
+DT_CHOSEN_Z_CONSOLE := zephyr,console
+DT_COMPAT_Z_CDC_ACM_UART := zephyr,cdc-acm-uart
+DT_COMPAT_STM32_USB := st,stm32-usb
+
+# Macros to shorten Kconfig expressions
+DT_CHOSEN_CONSOLE_NODE := $(dt_chosen_path,$(DT_CHOSEN_Z_CONSOLE))
+DT_CHOSEN_CONSOLE_PARENT := $(dt_node_parent,$(DT_CHOSEN_CONSOLE_NODE))
+
+if BOARD_XIAO_STM32C5 && \
+	$(dt_chosen_enabled,$(DT_CHOSEN_Z_CONSOLE)) && \
+	$(dt_compat_on_bus,$(DT_COMPAT_Z_CDC_ACM_UART),usb) && \
+	$(dt_node_has_compat,$(DT_CHOSEN_CONSOLE_PARENT),$(DT_COMPAT_STM32_USB))
+
+config CDC_ACM_SERIAL_SELF_POWERED
+	default n
+	depends on USB_DEVICE_STACK_NEXT && USBD_CDC_ACM_CLASS
+
+config CDC_ACM_SERIAL_MAX_POWER
+	default 250 if BOARD_XIAO_STM32C5	# 500mA
+	depends on USB_DEVICE_STACK_NEXT && USBD_CDC_ACM_CLASS
+
+# Logger cannot use itself to log
+choice USBD_CDC_ACM_LOG_LEVEL_CHOICE
+	default USBD_CDC_ACM_LOG_LEVEL_OFF
+	depends on LOG && USB_DEVICE_STACK_NEXT && USBD_CDC_ACM_CLASS
+endchoice
+
+# Set USB log level to error only
+choice USBD_LOG_LEVEL_CHOICE
+	default USBD_LOG_LEVEL_OFF
+	depends on LOG && USB_DEVICE_STACK_NEXT && USBD_CDC_ACM_CLASS
+endchoice
+
+# Set UDC driver log level to error only
+choice UDC_DRIVER_LOG_LEVEL_CHOICE
+	default UDC_DRIVER_LOG_LEVEL_ERR
+	depends on LOG && USB_DEVICE_STACK_NEXT && USBD_CDC_ACM_CLASS
+endchoice
+
+endif # zephyr,cdc-acm-uart
+
+# Revert USB CDC-ACM console via common fragment in upstream board.
+config BOARD_REQUIRES_SERIAL_BACKEND_CDC_ACM
+	default n if BOARD_XIAO_STM32C5_STM32C5A3XX_BBE && \
+	             !$(dt_compat_enabled,$(DT_COMPAT_STM32_USB))
+
+config BOARD_SERIAL_BACKEND_CDC_ACM
+	default n if BOARD_XIAO_STM32C5_STM32C5A3XX_BBE && \
+	             !$(dt_compat_enabled,$(DT_COMPAT_STM32_USB))
+
+# END of Revert USB CDC-ACM console (do not remove or change this line)

boards/seeed/xiao_stm32c5/Kconfig.xiao_stm32c5

@@ -0,0 +1,9 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 TiaC Systems
+# SPDX-License-Identifier: Apache-2.0
+
+config BOARD_XIAO_STM32C5_STM32C5A3XX
+	bool
+
+config BOARD_XIAO_STM32C5_STM32C5A3XX_BBE
+	bool
+	select BOARD_XIAO_STM32C5_STM32C5A3XX

boards/seeed/xiao_stm32c5/board.yml

@@ -0,0 +1,8 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 TiaC Systems
+# SPDX-License-Identifier: Apache-2.0
+
+board:
+  extend: xiao_stm32c5
+  variants:
+    - name: bbe
+      qualifier: stm32c5a3xx