目录层次：
====================
/arch Architecture specific files 体系结构专有文件
/arm Files generic to ARM architecture ARM体系的文件
/cpu CPU specific files CPU专有文件
/arm720t Files specific to ARM 720 CPUs ARM720t专有文件
/arm920t Files specific to ARM 920 CPUs ARM920t专有文件
/s3c24x0 Files specific to Samsung S3C24X0 CPUs 三星S3C24X0 CPU专有文件
……
/lib Architecture specific library files 体系结构专有库文件
/avr32 Files generic to AVR32 architecture
/cpu CPU specific files
/lib Architecture specific library files
……
/api Machine/arch independent API for external apps 外部程序使用的与体系无关的API
/board Board dependent files 开发板相关文件
/common Misc architecture independent functions 各种体系无关的功能
/disk Code for disk drive partition handling 磁盘分区处理的代码
/doc Documentation (don't expect too much) 文档（不要希望太多）
/drivers Commonly used device drivers 常用的设备驱动
/examples Example code for standalone applications, etc. 独立应用的示例代码
/fs Filesystem code (cramfs, ext2, jffs2, etc.) 文件系统代码
/include Header Files 头文件
/lib Files generic to all architectures 所有体系共有的文件
/libfdt Library files to support flattened device trees 支持flattened设备树的库
/lzma Library files to support LZMA decompression 支持LAMA解压的库
/lzo Library files to support LZO decompression 支持LZO解压的库
/net Networking code 网络代码
/post Power On Self Test 开机自检
/rtc Real Time Clock drivers 实时时钟驱动
/tools Tools to build S-Record or U-Boot images, etc. 创建S-Record和U-Boot镜像的工具
Software Configuration:
软件配置：
=======================
Configuration is usually done using C preprocessor defines; the rationale behind that is to avoid dead code whenever possible.
配置通常使用C预处理器的宏定义；这样做的合理性在于可以避免任何可能的死代码。
There are two classes of configuration variables:
有两种类型的可配置变量：
* Configuration _OPTIONS_:
These are selectable by the user and have names beginning with "CONFIG_".
这些配置是用户可选的，以"CONFIG_"开头命名
* Configuration _SETTINGS_:
These depend on the hardware etc. and should not be meddled with if you don't know what you're doing; they have names beginning with "CONFIG_SYS_".
这些配置依赖于硬件等，如果你不知道你在做什么的话，请不要干预，这些配置以"CONFIG_SYS_"开头。
Later we will add a configuration tool - probably similar to or even identical to what's used for the Linux kernel. Right now, we have to do the configuration by hand, which means creating some symbolic links and editing some configuration files. We use the TQM8xxL boards as an example here.
以后我们会添加一个配置工具 - 可能和Linux内核使用的类似甚至完全相同。但是目前我们还必须手工配置，这意味着需要创建一些符号链接并且编写一些配置文件。我们这里使用TQM8xxL开发板作为示例。