drivers: hdlc_rcp_if: Add HDLC SPI adapter driver

Implement the HDLC over SPI adapter driver to support the Openthread RCP
with SPI communication.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>

Author: pdgendt

drivers/hdlc_rcp_if/CMakeLists.txt

@@ -3,4 +3,5 @@
 zephyr_library()
 
 zephyr_library_sources_ifdef(CONFIG_HDLC_RCP_IF_NXP hdlc_rcp_if_nxp.c)
+zephyr_library_sources_ifdef(CONFIG_HDLC_RCP_IF_SPI hdlc_rcp_if_spi.c)
 zephyr_library_sources_ifdef(CONFIG_HDLC_RCP_IF_UART hdlc_rcp_if_uart.c)

drivers/hdlc_rcp_if/Kconfig

@@ -15,6 +15,7 @@ menuconfig HDLC_RCP_IF
 if HDLC_RCP_IF
 
 source "drivers/hdlc_rcp_if/Kconfig.nxp"
+source "drivers/hdlc_rcp_if/Kconfig.spi"
 source "drivers/hdlc_rcp_if/Kconfig.uart"
 
 config HDLC_RCP_IF_DRV_NAME

drivers/hdlc_rcp_if/Kconfig.spi

@@ -0,0 +1,34 @@
+# Configuration options for NXP HDLC RCP SPI communication Interface
+
+# Copyright (c) 2025 Basalte bv
+# SPDX-License-Identifier: Apache-2.0
+
+config HDLC_RCP_IF_SPI
+	bool "SPI HDLC interface for Zephyr Openthread RCP host"
+	default y
+	depends on DT_HAS_SPI_HDLC_RCP_IF_ENABLED
+	depends on SPI
+
+if HDLC_RCP_IF_SPI
+
+config HDLC_RCP_IF_SPI_MAX_FRAME_SIZE
+	int "HDLC RCP IF SPI maximum frame size"
+	default 2048
+	help
+	  Maximum frame size for the OpenThread HDLC host SPI.
+
+config HDLC_RCP_IF_SPI_ALIGN_ALLOWANCE
+	int "HDLC RCP IF SPI RX align allowance"
+	default 0
+	range 0 16
+	help
+	  Specify the maximum number of 0xFF bytes to clip from the start of MISO frames.
+
+config HDLC_RCP_IF_SPI_SMALL_PACKET_SIZE
+	int "HDLC RCP IF SPI small packet size"
+	default 32
+	help
+	  Specify the smallest packet we can receive in a single transaction.
+	  Larger packets will require multiple transactions.
+
+endif