问题遇到的现象和发生背景

linux 移植（boot+kenerl+rootfs），烧录镜像后后串口监控启动信息
1.切换控制台失败;
[ TIME ] Timed out waiting for device dev-ttyS0.device. [DEPEND] Dependency failed for Serial Getty on ttyS0.

问题相关代码，请勿粘贴截图

[ OK ] Stopped Getty on tty1.
[ OK ] Started Getty on tty1.
[ OK ] Stopped Getty on tty1.
[ OK ] Started Getty on tty1.
[ OK ] Stopped Getty on tty1.
[ OK ] Started Getty on tty1.
[ OK ] Stopped Getty on tty1.
[ OK ] Started Getty on tty1.
[ TIME ] Timed out waiting for device dev-ttyS0.device.
[DEPEND] Dependency failed for Serial Getty on ttyS0.
[ OK ] Reached target Login Prompts.
[ OK ] Reached target Multi-User System.
Starting Update UTMP about System Runlevel Changes.
[ OK ] Started Update UTMP about System Runlevel Changes.

我的解答思路和尝试过的方法

尝试过网上推荐的方法，无效果
Steps

1. First copy the template:

   cp /usr/lib/systemd/system/serial-getty@.service /etc/systemd/system/serial-getty@ttyS0.service

2. Then edit the file and modify the agetty line:
   [Service]
   ExecStart=-/sbin/agetty --keep-baud 115200,38400,9600 %I $TERM <-- Change this parameter
   Type=idle
3. Create a symlink:

   ln -s /etc/systemd/system/serial-getty@ttyS0.service /etc/systemd/system/getty.target.wants/