How to set different defaults for Kconfig values like `CONFIG_USBDEBUG_DEFAULT_PORT`

[Paul Menzel]

Dear coreboot folks,

looking at how to split up the patch for the Lenovo X201 southbridge
support [1],

commit 92ba16cf9fabcf478c225dff687ae717666b502d
        Author: Vladimir Serbinenko 
        Date:   Sun Mar 31 22:22:10 2013 +0200

intel/bd82x6x: Support mobile 5 southbridge

I stumbled over `CONFIG_USBDEBUG_DEFAULT_PORT`.

$ git describe
        4.0-3936-g92ba16c
        $ git grep -A3 USBDEBUG_DEFAULT_PORT
        src/console/Kconfig:config USBDEBUG_DEFAULT_PORT
        src/console/Kconfig-    int "Default USB port to use as Debug Port"
        src/console/Kconfig-    default 1
        src/console/Kconfig-    depends on USBDEBUG && !SOUTHBRIDGE_INTEL_I82801GX && !SOUTHBRIDGE_AMD_SB600
        --
        src/console/console.c:  enable_usbdebug(CONFIG_USBDEBUG_DEFAULT_PORT);
        src/console/console.c-  early_usbdebug_init();
        src/console/console.c-#endif
        src/console/console.c-#if CONFIG_CONSOLE_SERIAL
        --
        src/southbridge/amd/sb600/Kconfig:config USBDEBUG_DEFAULT_PORT
        src/southbridge/amd/sb600/Kconfig-      int
        src/southbridge/amd/sb600/Kconfig-      default 0
        src/southbridge/amd/sb600/Kconfig-
        --
        src/southbridge/intel/bd82x6x/Kconfig:config USBDEBUG_DEFAULT_PORT
        src/southbridge/intel/bd82x6x/Kconfig-  int
        src/southbridge/intel/bd82x6x/Kconfig-  default 2
        src/southbridge/intel/bd82x6x/Kconfig-
        --
        src/southbridge/intel/i82801gx/Kconfig:config USBDEBUG_DEFAULT_PORT
        src/southbridge/intel/i82801gx/Kconfig- int
        src/southbridge/intel/i82801gx/Kconfig- default 1
        src/southbridge/intel/i82801gx/Kconfig-
        --
        src/southbridge/intel/i82801ix/Kconfig:config USBDEBUG_DEFAULT_PORT
        src/southbridge/intel/i82801ix/Kconfig- int
        src/southbridge/intel/i82801ix/Kconfig- default 1
        src/southbridge/intel/i82801ix/Kconfig-

1. Is there an easier way to handle this? I assume the complexity is due
to the fact, that boards have different defaults?

Is default

default 1
        default 0 if SOUTHBRIDGE_AMD_SB600

a shorter alternative?

2. The other thing is probably under what menu item this option is
displayed at. If under Console or Chipset.

Do you have other suggestions? Shall I prepare a commit to change the
code as suggested above?

Thanks,

Paul

[1] http://review.coreboot.org/#/c/2995/