soc/intel/common/block/smm: Add option to have SOC specific SMI Handler at finalize()

This patch ensures common code provides an option to register a
SOC specific SMI handler before booting to OS (specifically during ramstage).

Change-Id: I50fb154cc1ad4b3459bc352d2065f2c582711c20
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/23810
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Tung Lun Loo <tung.lun.loo@intel.com>

src/soc/intel/common/block/include/intelblocks/smihandler.h

@@ -148,6 +148,9 @@ struct global_nvs_t *smm_get_gnvs(void);
 
 /* SoC overrides. */
 
+/* Specific SOC SMI handler during ramstage finalize phase */
+void smihandler_soc_at_finalize(void);
+
 /*
  * This function returns a 1 or 0 depending on whether disable_busmaster
  * needs to be done for the specified device on S5 entry

src/soc/intel/common/block/smm/smihandler.c

@@ -38,6 +38,12 @@ static struct global_nvs_t *gnvs;
 
 /* SoC overrides. */
 
+/* Specific SOC SMI handler during ramstage finalize phase */
+__attribute__((weak)) void smihandler_soc_at_finalize(void)
+{
+	return;
+}
+
 __attribute__((weak)) int smihandler_soc_disable_busmaster(device_t dev)
 {
 	return 1;
@@ -278,6 +284,9 @@ static void finalize(void)
 	if (IS_ENABLED(CONFIG_SPI_FLASH_SMM))
 		/* Re-init SPI driver to handle locked BAR */
 		fast_spi_init();
+
+	/* Specific SOC SMI handler during ramstage finalize phase */
+	smihandler_soc_at_finalize();
 }
 
 void smihandler_southbridge_apmc(