dt-bindings: ata: ahci: Add platform capability properties

In case if the platform doesn't have BIOS or a comprehensive firmware
installed then the HBA capability flags will be left uninitialized. As a
good alternative we suggest to define the DT-properties with the AHCI
platform capabilities describing all the HW-init flags of the
corresponding capability register. Luckily there aren't too many of them.
SSS - Staggered Spin-up support and MPS - Mechanical Presence Switch
support determine the corresponding feature availability for the whole HBA
by means of the "hba-cap" property. Each port can have the "hba-port-cap"
property initialized indicating that the port supports some of the next
functionalities: HPCP - HotPlug capable port, MPSP - Mechanical Presence
Switch attached to a port, CPD - Cold Plug detection, ESP - External SATA
Port (eSATA), FBSCP - FIS-based switching capable port.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

include/dt-bindings/ata/ahci.h

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause */
+/*
+ * This header provides constants for most AHCI bindings.
+ */
+
+#ifndef _DT_BINDINGS_ATA_AHCI_H
+#define _DT_BINDINGS_ATA_AHCI_H
+
+/* Host Bus Adapter generic platform capabilities */
+#define HBA_SSS		(1 << 27)
+#define HBA_SMPS	(1 << 28)
+
+/* Host Bus Adapter port-specific platform capabilities */
+#define HBA_PORT_HPCP	(1 << 18)
+#define HBA_PORT_MPSP	(1 << 19)
+#define HBA_PORT_CPD	(1 << 20)
+#define HBA_PORT_ESP	(1 << 21)
+#define HBA_PORT_FBSCP	(1 << 22)
+
+#endif