mailbox: pcc: Add PCC request and free channel declarations

Exports pcc_mbox_request_channel() and pcc_mbox_free_channel()
declarations into a pcc.h header file.

Looks-good-to: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Hoan Tran <hotran@apm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/include/acpi/pcc.h b/include/acpi/pcc.h
new file mode 100644
index 0000000..17a940a
--- /dev/null
+++ b/include/acpi/pcc.h
@@ -0,0 +1,29 @@
+/*
+ * PCC (Platform Communications Channel) methods
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#ifndef _PCC_H
+#define _PCC_H
+
+#include <linux/mailbox_controller.h>
+#include <linux/mailbox_client.h>
+
+#ifdef CONFIG_PCC
+extern struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
+						  int subspace_id);
+extern void pcc_mbox_free_channel(struct mbox_chan *chan);
+#else
+static inline struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
+							 int subspace_id)
+{
+	return NULL;
+}
+static inline void pcc_mbox_free_channel(struct mbox_chan *chan) { }
+#endif
+
+#endif /* _PCC_H */