how to download ubuntu kernel and patch it

gistfile1.txt

sudo apt-get install dpkg-dev
#https://askubuntu.com/questions/496549/error-you-must-put-some-source-uris-in-your-sources-list
sudo apt-get build-dep gawk
sudo nano /etc/apt/sources.list
deb-src http://security.ubuntu.com/ubuntu bionic-security main
sudo apt-get source linux-souce...
apt-get source linux #why this works??
sudo apt-get build-dep linux-image-$(uname -r)
tar -xzvf archive.tar.gz
cd kernel_source_directory
patch -p1 < diff_file_path
chmod +x debian/rules
fakeroot debian/rules clean
fakeroot debian/rules binary-headers binary-generic binary-perarch