add raspi4 32bit mode bsp

bsp/raspberry-pi/raspi4-32/driver/board.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2006-2020, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author         Notes
+ * 2020-04-16     bigmagic       first version
+ */
+
+#ifndef BOARD_H__
+#define BOARD_H__
+
+#include <stdint.h>
+#include "raspi4.h"
+
+extern unsigned char __bss_start;
+extern unsigned char __bss_end;
+
+#define RT_HW_HEAP_BEGIN    (void*)&__bss_end
+#define RT_HW_HEAP_END      (void*)(RT_HW_HEAP_BEGIN + 64 * 1024 * 1024)
+
+void rt_hw_board_init(void);
+
+#endif