drivers: serial: silabs: introduce asynchronous silabs eusart

Introduce silabs asynchronous eusart with dma support.

Signed-off-by: Martin Hoff <martin.hoff@silabs.com>

Author: Martinhoff-maker

drivers/serial/Kconfig.silabs_eusart

@@ -1,4 +1,5 @@
 # Copyright (c) 2024, Yishai Jaffe
+# Copyright (c) 2025, Silicon Laboratories Inc.
 # SPDX-License-Identifier: Apache-2.0
 
 config UART_SILABS_EUSART
@@ -8,8 +9,23 @@ config UART_SILABS_EUSART
 	select SERIAL_HAS_DRIVER
 	select SERIAL_SUPPORT_INTERRUPT
 	select SOC_GECKO_EUSART
+	select SERIAL_SUPPORT_ASYNC \
+		if DT_HAS_SILABS_LDMA_ENABLED
+	select DMA if UART_ASYNC_API
 	select PINCTRL
 	select CLOCK_CONTROL
 	select PM_DEVICE if PM
 	help
 	  Enable the eusart uart driver.
+
+if UART_SILABS_EUSART
+
+config UART_SILABS_EUSART_ASYNC
+	bool
+	depends on DMA_SILABS_LDMA
+	depends on UART_ASYNC_API
+	default y
+	help
+	  If 'y', Silabs eusart driver will compile with support for UART async API.
+
+endif