Linux and Android are separate operating systems now, but that may change since Android code has been re-admitted to a staging area for inclusion the Linux kernel, according to an article by Cade Metz for Wired Enterprise, "Android and Linux Reunite After Two-Year Separation."
Metz quotes The Linux Foundation's Greg Kroah-Hartman as saying that a number of companies are now working to merge the Android code into the main Linux tree and that "for something like this, that is so useful to so many users of Linux, it should be in the kernel tree to help make future releases easier for us and the Android developers."