riscv: Add support for Espressif Direct Boot

This adds the ability to generate a binary image with an Espressif
Direct Boot header.

bsps/riscv/shared/start/start.S

@@ -42,6 +42,16 @@ PUBLIC(_start)
 	.option	arch, +zicsr
 	.option	norelax
 
+#ifdef ESPRESSIF_DIRECT_BOOT
+/*
+ * These header values indicate to the ESP32 bootrom that the application in
+ * flash is to be run via direct boot and is not an application image to be
+ * unpacked.
+ */
+	.word 0xaedb041d
+	.word 0xaedb041d
+#endif
+
 TYPE_FUNC(_start)
 SYM(_start):
 

spec/build/bsps/riscv/optespressifdirectboot.yml

@@ -0,0 +1,19 @@
+SPDX-License-Identifier: CC-BY-SA-4.0 OR BSD-2-Clause
+actions:
+- get-boolean: null
+- env-enable: null
+- define-condition: null
+build-type: option
+copyrights:
+- Copyright (C) 2026 Kinsey Moore <wkmoore@gmail.com>
+default:
+- enabled-by: riscv/esp32c3db
+  value: true
+- enabled-by: true
+  value: false
+description: |
+  Enable direct boot for Espressif chips
+enabled-by: true
+links: []
+name: ESPRESSIF_DIRECT_BOOT
+type: build