v4.19.13 snapshot.
diff --git a/include/linux/irqchip.h b/include/linux/irqchip.h
new file mode 100644
index 0000000..89c34b2
--- /dev/null
+++ b/include/linux/irqchip.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2012 Thomas Petazzoni
+ *
+ * Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#ifndef _LINUX_IRQCHIP_H
+#define _LINUX_IRQCHIP_H
+
+#include <linux/acpi.h>
+#include <linux/of.h>
+
+/*
+ * This macro must be used by the different irqchip drivers to declare
+ * the association between their DT compatible string and their
+ * initialization function.
+ *
+ * @name: name that must be unique accross all IRQCHIP_DECLARE of the
+ * same file.
+ * @compstr: compatible string of the irqchip driver
+ * @fn: initialization function
+ */
+#define IRQCHIP_DECLARE(name, compat, fn) OF_DECLARE_2(irqchip, name, compat, fn)
+
+/*
+ * This macro must be used by the different irqchip drivers to declare
+ * the association between their version and their initialization function.
+ *
+ * @name: name that must be unique accross all IRQCHIP_ACPI_DECLARE of the
+ * same file.
+ * @subtable: Subtable to be identified in MADT
+ * @validate: Function to be called on that subtable to check its validity.
+ * Can be NULL.
+ * @data: data to be checked by the validate function.
+ * @fn: initialization function
+ */
+#define IRQCHIP_ACPI_DECLARE(name, subtable, validate, data, fn) \
+ ACPI_DECLARE_PROBE_ENTRY(irqchip, name, ACPI_SIG_MADT, \
+ subtable, validate, data, fn)
+
+#ifdef CONFIG_IRQCHIP
+void irqchip_init(void);
+#else
+static inline void irqchip_init(void) {}
+#endif
+
+#endif