mb/google/guybrush: Add new mainboard

Guybrush is a new Google mainboard with an AMD SOC.

BUG=b:175143925
TEST=builds

Change-Id: I1792f21ff7616f364ddc8b0c04481049b2a5fb04
Signed-off-by: Mathew King <mathewk@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48479
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/google/guybrush/variants/baseboard/devicetree.cb b/src/mainboard/google/guybrush/variants/baseboard/devicetree.cb
new file mode 100644
index 0000000..519bd07
--- /dev/null
+++ b/src/mainboard/google/guybrush/variants/baseboard/devicetree.cb
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+chip soc/amd/cezanne
+	device domain 0 on
+	end # domain
+end	# chip soc/amd/cezanne