For systems based on glibc, there are no specific guidelines for this directory. For systems based on Linux libc revisions prior to glibc, the following guidelines and rationale apply:
The only source code that should be placed in a specific location is the Linux kernel source code. It is located in /usr/src/linux.
If a C or C++ compiler is installed, but the complete Linux kernel source code is not installed, then the include files from the kernel source code shall be located in these directories:
/usr/src/linux/include/asm-<arch> /usr/src/linux/include/linux
<arch> is the name of the system architecture.
Note: /usr/src/linux may be a symbolic link to a kernel source code tree.