payloads/external: Add support for coreDOOM payload

coreDOOM is a port of DOOM to libpayload, based on the doomgeneric
source port. It renders the game to the coreboot linear framebuffer,
and loads WAD files from CBFS.

Tested with QEMU i440fx/q35 and a Dell Latitude E6400 using the
libgfxinit provided linear framebuffer.

Project page: https://github.com/nic3-14159/coreDOOM

Signed-off-by: Nicholas Chin <nic.c3.14@gmail.com>
Change-Id: Ice0403b003a4b2717afee585f28303c2f5abea5d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57222
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Martin L Roth <gaumless@tutanota.com>
diff --git a/payloads/Kconfig b/payloads/Kconfig
index e184b35..2e627d7 100644
--- a/payloads/Kconfig
+++ b/payloads/Kconfig
@@ -165,6 +165,16 @@
 	  tint can be loaded as a secondary payload under SeaBIOS, GRUB,
 	  or any other payload that can load additional payloads.
 
+config COREDOOM_SECONDARY_PAYLOAD
+	bool "Load coreDOOM as a secondary payload"
+	default n
+	depends on ARCH_X86
+	help
+	  coreDOOM can be loaded as a secondary payload under SeaBIOS, GRUB,
+	  or any other payload that can load additional payloads. Requires a
+	  linear framebuffer. If built as a secondary payload for SeaBIOS, the
+	  generated VGA BIOS option rom is also required.
+
 source "payloads/external/*/Kconfig.secondary"
 
 endmenu # "Secondary Payloads"