NFC: Sony Port-100 Series driver

This adds support for the Sony NFC USB dongle RC-S380, based on the
Port-100 chip. This dongle is an analog frontend and does not implement
the digital layer. This driver uses the nfc_digital module which is an
implementation of the NFC Digital Protocol stack.

This patch is a skeleton. It only registers the dongle against the NFC
digital protocol stack. All NFC digital operation functions are stubbed
out.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Cc: Stephen Tiedemann <stephen.tiedemann@gmail.com>
Tested-by: Cho, Yu-Chen <acho@suse.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/nfc/Kconfig b/drivers/nfc/Kconfig
index b0b64cc..c1fb206 100644
--- a/drivers/nfc/Kconfig
+++ b/drivers/nfc/Kconfig
@@ -46,6 +46,16 @@
 
 	  If unsure, say N.
 
+config NFC_PORT100
+	tristate "Sony NFC Port-100 Series USB device support"
+	depends on USB
+	depends on NFC_DIGITAL
+	help
+	  This adds support for Sony Port-100 chip based USB devices such as the
+	  RC-S380 dongle.
+
+	  If unsure, say N.
+
 source "drivers/nfc/pn544/Kconfig"
 source "drivers/nfc/microread/Kconfig"