ACPI: Add framework for GNVS initialisation

Provide common initialisation point for setting up
GNVS structure before first SMI is triggered.

Change-Id: Iccad533c3824d70f6cbae52cc8dd79f142ece944
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42423
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/acpi/acpi_gnvs.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ACPI_GNVS_H__
+#define __ACPI_GNVS_H__
+
+#include <types.h>
+
+void *acpi_get_gnvs(void);
+void *gnvs_get_or_create(void);
+void acpi_inject_nvsa(void);
+
+void gnvs_assign_chromeos(void);
+
+/* Platform code must implement these. */
+size_t gnvs_size_of_array(void);
+uint32_t *gnvs_cbmc_ptr(void);
+void *gnvs_chromeos_ptr(void);
+
+#endif