App: Add NS interface code moved from TF-M

Add NS interface code moved from TF-M. It includes OS wrapper headers
and RTX specific implementation of OS wrapper.

Signed-off-by: David Hu <david.hu@arm.com>
Change-Id: I0b88535eaa720b52d2090d5ed041987093df9d75
diff --git a/ns_interface/os_wrapper/thread.h b/ns_interface/os_wrapper/thread.h
new file mode 100644
index 0000000..a493593
--- /dev/null
+++ b/ns_interface/os_wrapper/thread.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2017-2020, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#ifndef __OS_WRAPPER_THREAD_H__
+#define __OS_WRAPPER_THREAD_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "common.h"
+
+/* prototype for the thread entry function */
+typedef void (*os_wrapper_thread_func) (void *argument);
+
+/**
+ * \brief Creates a new thread
+ *
+ * \param[in] name        Name of the thread
+ * \param[in] stack_size  Size of stack to be allocated for this thread. It can
+ *                        be \ref OS_WRAPPER_DEFAULT_STACK_SIZE to use the
+ *                        default value provided by the underlying RTOS
+ * \param[in] func        Pointer to the function invoked by thread
+ * \param[in] arg         Argument to pass to the function invoked by thread
+ * \param[in] priority    Initial thread priority
+ *
+ * \return Returns the thread handle created, or NULL in case of error
+ */
+void *os_wrapper_thread_new(const char *name, int32_t stack_size,
+                            os_wrapper_thread_func func, void *arg,
+                            uint32_t priority);
+/**
+ * \brief Gets current thread handle
+ *
+ * \return Returns the thread handle, or NULL in case of error
+ */
+void *os_wrapper_thread_get_handle(void);
+
+/**
+ * \brief Gets thread priority
+ *
+ * \param[in]  handle   Thread handle
+ * \param[out] priority The priority of the thread
+ *
+ * \return Returns \ref OS_WRAPPER_SUCCESS on success, or \ref OS_WRAPPER_ERROR
+ *                 in case of error
+ */
+uint32_t os_wrapper_thread_get_priority(void *handle, uint32_t *priority);
+
+/**
+ * \brief Exits the calling thread
+ */
+void os_wrapper_thread_exit(void);
+
+/**
+ * \brief Set the event flags for synchronizing a thread specified by handle.
+ *
+ * \note This function may not be allowed to be called from Interrupt Service
+ *       Routines.
+ *
+ * \param[in] handle    Thread handle to be notified
+ * \param[in] flags     Event flags value
+ *
+ * \return Returns \ref OS_WRAPPER_SUCCESS on success, or \ref OS_WRAPPER_ERROR
+ *         in case of error
+ */
+uint32_t os_wrapper_thread_set_flag(void *handle, uint32_t flags);
+
+/**
+ * \brief Set the event flags in an interrupt handler for synchronizing a thread
+ *        specified by handle.
+ *
+ * \param[in] handle    Thread handle to be notified
+ * \param[in] flags     Event flags value
+ *
+ * \return Returns \ref OS_WRAPPER_SUCCESS on success, or \ref OS_WRAPPER_ERROR
+ *         in case of error
+ */
+uint32_t os_wrapper_thread_set_flag_isr(void *handle, uint32_t flags);
+
+/**
+ * \brief Wait for the event flags for synchronizing threads.
+ *
+ * \note This function may not be allowed to be called from Interrupt Service
+ *       Routines.
+ *
+ * \param[in] flags     Specify the flags to wait for
+ * \param[in] timeout   Timeout value
+ *
+ * \return Returns \ref OS_WRAPPER_SUCCESS on success, or \ref OS_WRAPPER_ERROR
+ *         in case of error
+ */
+uint32_t os_wrapper_thread_wait_flag(uint32_t flags, uint32_t timeout);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __OS_WRAPPER_THREAD_H__ */