I have a .fex file for Cubietruck. Supposedly, the bluetooth pins are defined in the uart_para2. With the current config, I have uart0 and uart2 enabled, and everything else is disabled. Bluetooth functions fine under such condition.
Then, I changed the .fex file by simply renaming [uart_para2] to [uart_para3] and vice-verca (renaming uart3 to uart2). The new "uart2" (or the old "uart3") is still disabled.
Now bluetooth does not work anymore. dmesg | grep tty still shows that uart3 is mounted on /dev/ttyS1.
So what is UART and why does the label matter? I thought it's a label and nothing more, but evidently not.