[serial]增加at32的serial_v2驱动

bsp/at32/libraries/rt_drivers/SConscript

@@ -16,8 +16,11 @@ if GetDepend(['RT_USING_PIN']):
 if GetDepend(['RT_USING_WDT']):
     src += ['drv_wdt.c']
 
-if GetDepend(['BSP_USING_SERIAL']):
-    src += ['drv_usart.c']
+if GetDepend(['RT_USING_SERIAL']):
+    if GetDepend(['RT_USING_SERIAL_V2']):
+        src += ['drv_usart_v2.c']
+    else:
+        src += ['drv_usart.c']
 
 if GetDepend(['BSP_USING_PWM']):
     src += ['drv_pwm.c']

bsp/at32/libraries/rt_drivers/drv_usart_v2.h

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2006-2021, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2023-02-23     Jonas        first version
+ */
+
+#ifndef __DRV_USART_V2_H__
+#define __DRV_USART_V2_H__
+
+#include <rtthread.h>
+#include <rtdevice.h>
+#include <drv_common.h>
+
+struct at32_usart
+{
+    char *name;
+    usart_type *usart_x;
+    IRQn_Type irqn;
+    struct rt_serial_device serial;
+};
+
+int rt_hw_usart_init(void);
+
+#endif /* __DRV_USART_V2_H__ */