diff --git a/include/nvidia-oot/dt-bindings/mailbox/tegra186-hsp-oot.h b/include/nvidia-oot/dt-bindings/mailbox/tegra186-hsp-oot.h
new file mode 100644
index 0000000..4434bdb
--- /dev/null
+++ b/include/nvidia-oot/dt-bindings/mailbox/tegra186-hsp-oot.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * This header provides constants for binding nvidia,tegra186-hsp.
+ */
+
+#ifndef _DT_BINDINGS_MAILBOX_TEGRA186_HSP_OOT_H
+#define _DT_BINDINGS_MAILBOX_TEGRA186_HSP_OOT_H
+
+#include <dt-bindings/mailbox/tegra186-hsp.h>
+
+/*
+ * These define the types of shared mailbox supported based on data size.
+ */
+#ifdef TEGRA_HSP_MBOX_TYPE_SM_128BIT
+#undef TEGRA_HSP_MBOX_TYPE_SM_128BIT
+#endif
+
+#define TEGRA_HSP_MBOX_TYPE_SM_128BIT 0x4
+
+/*
+ * Shared interrupt source, mapped with mailboxes
+ */
+#define TEGRA_HSP_SHARED_IRQ_MASK 0xffff0000
+#define TEGRA_HSP_SHARED_IRQ_OFFSET (16)
+#define TEGRA_HSP_SHARED_IRQ(x) (((x) << TEGRA_HSP_SHARED_IRQ_OFFSET) & TEGRA_HSP_SHARED_IRQ_MASK)
+
+#endif