title: How can I set U-boot CONFIG_MYBOARD_XXXX values from the command line?
body: <p>I'm working on custom hardware, and have added a new <code>myboard</code> board to my U-boot repro. The <code>make</code> pattern is very standard:</p>
  
  <pre><code>make myboard_defconfig
  make
  </code></pre>
  
  <p>which sets the U-Boot configuration to the myboard defaults, and then builds the resulting U-boot image. It all works, but I need to take it one step further.</p>
  
  <p>The hardware actually comes in two closely-related flavors, and I need to build slightly different U-Boot images for the two flavors. Rather than defining two completely different boards, I'd like to build the same board type twice, but with a <code>CONFIG_MYBOARD_XXXX</code> symbol having different values. My <code>myboard.c</code> file will then have an <code>#if CONFIG_MYBOARD_XXXX == YYYY</code> test to differentiate the results.</p>
  
  <p>Problem: I want to set <code>CONFIG_MYBOARD_XXXX</code>'s value from within my parent <code>Makefile</code>, not by running anything interactive like <code>make menuconfig</code>.</p>
  
  <p>What's the "right" way to do this?</p>