title: How to output pr_info() information with linux kernel startup
body: <p>When the kernel boots, messages will be output to the serial port.</p>
  <p>If <code>printk(&quot;Information&quot;)</code> is called, the &quot;Information&quot; will be displayed by the serial port.</p>
  <p>I want to display all the <code>pr_info（“”)</code> information in Linux Kernel by serial port. How to build the kernel?</p>