shell: move shell to its own subsystem

This moves the shell component into its own subsys and groups all
related files and options into a single place.

Additionally, one Kconfig option will now be required to enable the
shell:

 CONFIG_CONSOLE_SHELL=y

The header files was also moved to include/shell/shell.h and can be now
referenced with

 #include <shell/shell.h>

instead of

 #include <misc/shell.h>

Updated documentation as well.

Change-Id: Iffbba4acfa05408055e9fd28dffa213451351f94
Signed-off-by: Anas Nashif <anas.nashif@intel.com>

include/shell/shell.h

@@ -0,0 +1,133 @@
+/* shell.h - Shell header */
+
+/*
+ * Copyright (c) 2015 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+struct device;
+
+/** @brief Callback called when command is entered.
+ *
+ *  @param argc Number of parameters passed.
+ *  @param argv Array of option strings. First option is always command name.
+ *
+ * @return 0 in case of success or negative value in case of error.
+ */
+typedef int (*shell_cmd_function_t)(int argc, char *argv[]);
+
+struct shell_cmd {
+	const char *cmd_name;
+	shell_cmd_function_t cb;
+	const char *help;
+};
+
+
+struct shell_module {
+	const char *module_name;
+	const struct shell_cmd *commands;
+};
+
+
+/**
+ * @brief Kernel Shell API
+ * @defgroup _shell_api_functions Shell API Functions
+ * @{
+ */
+
+/**
+ * @def SHELL_REGISTER
+ *
+ * @brief Create shell_module object and set it up for boot time initialization.
+ *
+ * @details This macro defines a shell_module object that is automatically
+ * configured by the kernel during system initialization.
+ *
+ * @param shell_name Module name to be entered in shell console.
+ *
+ * @param shell_commands Array of commands to register.
+ * Shell array entries must be packed to calculate array size correctly.
+ */
+#ifdef CONFIG_CONSOLE_SHELL
+#define SHELL_REGISTER(shell_name, shell_commands) \
+	\
+	static struct shell_module (__shell_shell_name) __used \
+	__attribute__((__section__(".shell_"))) = { \
+		  .module_name = shell_name, \
+		  .commands = shell_commands \
+	}
+
+#else
+#define SHELL_REGISTER(shell_name, shell_commands)
+#endif
+
+/** @brief Initialize shell with optional prompt, NULL in case no prompt is
+ *         needed.
+ *
+ *  @param prompt Prompt to be printed on serial console.
+ */
+void shell_init(const char *prompt);
+
+/** @brief Optionally register an app default cmd handler.
+ *
+ *  @param handler To be called if no cmd found in cmds registered with
+ *  shell_init.
+ */
+void shell_register_app_cmd_handler(shell_cmd_function_t handler);
+
+/** @brief Callback to get the current prompt.
+ *
+ *  @returns Current prompt string.
+ */
+typedef const char *(*shell_prompt_function_t)(void);
+
+/** @brief Optionally register a custom prompt callback.
+ *
+ *  @param handler To be called to get the current prompt.
+ */
+void shell_register_prompt_handler(shell_prompt_function_t handler);
+
+/** @brief Optionally register a default module, to eliminate typing it in
+ *  shell console or for backwards compatibility.
+ *
+ *  @param name Module name.
+ */
+void shell_register_default_module(const char *name);
+
+/**
+* @}
+*/
+
+
+#ifdef CONFIG_CONSOLE_SHELL
+int shell_run(struct device *dev);
+#else
+static inline int shell_run(struct device *dev)
+{
+	ARG_UNUSED(dev);
+
+	return 0;
+}
+#endif
+
+
+#ifdef __cplusplus
+}
+#endif
+