tests: drivers: spi: spi_loopback: Enabled SPI in BTL-S

Added overlay and conf to enable SPI tests on BTL-S board.

Signed-off-by: Bindu S <[email protected]>

Author: bindushree98

tests/drivers/spi/spi_loopback/boards/intel_btl_s_crb.conf

@@ -0,0 +1,4 @@
+CONFIG_SPI=y
+CONFIG_SPI_ASYNC=n
+CONFIG_GPIO=y
+CONFIG_SPI_LOOPBACK_MODE_LOOP=y

tests/drivers/spi/spi_loopback/boards/intel_btl_s_crb.overlay

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2025 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/* External Loopback: Short MOSI (J7H4.3) & MISO (J7H4.5) */
+
+&gpio_0_i {
+	status = "okay";
+};
+
+&spi0 {
+	pw,cs-mode = <0>;
+	pw,cs-output = <0>;
+	status = "okay";
+
+	slow@0 {
+		compatible = "test-spi-loopback-slow";
+		reg = <0>;
+		spi-max-frequency = <500000>;
+	};
+	fast@0 {
+		compatible = "test-spi-loopback-fast";
+		reg = <0>;
+		spi-max-frequency = <16000000>;
+	};
+};