diff --git a/include/acpi/actbl1.h b/include/acpi/actbl1.h
index 556c83ee..4ec8c19 100644
--- a/include/acpi/actbl1.h
+++ b/include/acpi/actbl1.h
@@ -457,7 +457,7 @@
 	u8 enabled;
 	u32 records_to_preallocate;
 	u32 max_sections_per_record;
-	u32 bus;
+	u32 bus;		/* Bus and Segment numbers */
 	u16 device;
 	u16 function;
 	u16 device_control;
@@ -473,6 +473,14 @@
 #define ACPI_HEST_FIRMWARE_FIRST        (1)
 #define ACPI_HEST_GLOBAL                (1<<1)
 
+/*
+ * Macros to access the bus/segment numbers in Bus field above:
+ *  Bus number is encoded in bits 7:0
+ *  Segment number is encoded in bits 23:8
+ */
+#define ACPI_HEST_BUS(bus)              ((bus) & 0xFF)
+#define ACPI_HEST_SEGMENT(bus)          (((bus) >> 8) & 0xFFFF)
+
 /* Hardware Error Notification */
 
 struct acpi_hest_notify {