[FEATURE/FDT] Add bootargs select in early

Maybe use for memory/DMA buffer init before
ofw_node unflatten.

Signed-off-by: GuEe-GUI <2991707448@qq.com>

components/drivers/include/drivers/ofw_fdt.h

@@ -70,6 +70,7 @@ rt_err_t rt_fdt_boot_dump(void);
 void rt_fdt_earlycon_output(const char *str);
 void rt_fdt_earlycon_kick(int why);
 rt_err_t rt_fdt_scan_chosen_stdout(void);
+rt_err_t rt_fdt_bootargs_select(const char *key, int index, const char **out_result);
 rt_err_t rt_fdt_unflatten(void);
 
 struct rt_ofw_node *rt_fdt_unflatten_single(void *fdt);

components/drivers/ofw/fdt.c

@@ -793,6 +793,55 @@ rt_err_t rt_fdt_scan_chosen_stdout(void)
     return err;
 }
 
+rt_err_t rt_fdt_bootargs_select(const char *key, int index, const char **out_result)
+{
+    rt_err_t err;
+
+    if (key && index >= 0 && out_result)
+    {
+        int offset = fdt_path_offset(_fdt, "/chosen");
+
+        if (offset >= 0)
+        {
+            int len, key_len = rt_strlen(key);
+            const char *bootargs = fdt_getprop(_fdt, offset, "bootargs", &len), *end;
+
+            end = bootargs + len;
+            err = -RT_EEMPTY;
+
+            for (int i = 0; bootargs < end; ++i)
+            {
+                bootargs = rt_strstr(bootargs, key);
+
+                if (!bootargs)
+                {
+                    break;
+                }
+
+                bootargs += key_len;
+
+                if (i == index)
+                {
+                    *out_result = bootargs;
+
+                    err = -RT_EOK;
+                    break;
+                }
+            }
+        }
+        else
+        {
+            err = -RT_ERROR;
+        }
+    }
+    else
+    {
+        err = -RT_EINVAL;
+    }
+
+    return err;
+}
+
 static void system_node_init_flag(struct rt_ofw_node *np)
 {
     if (np)