方法一：
https://source.android.com/setup/building-kernels
方法二：
在按照https://source.android.com/setup/downloading中说的方法建立mirror后，其实kernel也已经在其中了：
这样我们就可以直接使用下面的命令本地下载需要的kernel了，以goldfish为例：
git clone /home/pengdonglin/disk_ext/Android_Latest/aosp_mirror/kernel/goldfish
然后取出自己需要的分支即可：
pengdonglin@pengdonglin-dell:~/Android_kernel/goldfish$ git co origin/android-goldfish-2.6.
Checking out files: % (/), done.
Note: checking out 'origin/android-goldfish-2.6.29'. You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout. If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example: git checkout -b <new-branch-name> HEAD is now at 4bb8fa0... goldfish: Add encrypted SD Card support.
pengdonglin@pengdonglin-dell:~/Android_kernel/goldfish$ ls
arch CREDITS drivers include Kbuild MAINTAINERS net samples sound
block crypto firmware init kernel Makefile README scripts usr
COPYING Documentation fs ipc lib mm REPORTING-BUGS security virt
方法三：
使用repo本地下载：
repo init -u /home/pengdonglin/disk_ext/Android_Latest/aosp_mirror/platform/manifest.git
然后修改.repo/manifest.xml为：
<?xml version="1.0" encoding="UTF-8"?>
<manifest> <remote name="aosp"
fetch=".."
review="https://android-review.googlesource.com/" />
<default revision="master"
remote="aosp"
sync-j="" /> <project path="goldfish" name="kernel/goldfish" /> </manifest>
即只填写一个project，当然如果有其他需要的project，也可以接着追加。
最后执行repo sync即可。
完。