meta: Introduce RT kernel patch

Signed-off-by: Kirill Kapranov <kirill.kapranov@compulab.co.il>

recipes-kernel/linux-rt/linux-imx_%.bbappend

@@ -0,0 +1,22 @@
+include rt.inc
+
+python (){
+    import re
+
+    if bb.utils.contains('IMAGE_FEATURES', 'realtime-kernel', False, True, d):
+        return
+
+    PV = d.getVar("PV")
+    major_dot_minor_dot_fix = re.sub(r'\+.*$', '',  PV)
+
+    rt_patch_uri = d.getVar('RT_PATCH_URI')
+    if re.search(r'patch-' + major_dot_minor_dot_fix + '-rt', rt_patch_uri):
+        d.appendVar("SRC_URI"," " + rt_patch_uri + " ")
+    else:
+        patch_name = re.search(r'^.*(patch-[\.0-9]*-rt[\.0-9]*\.patch).*$',rt_patch_uri)
+        if patch_name:
+            bb.error("RT patch: " + patch_name.group(1))
+            bb.error("Kernel revision to build: " + major_dot_minor_dot_fix)
+            bb.error("Please find an appropriate patch on https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt")
+        #bb.fatal("RT patch revision doesn't match the kernel revision we are about to build")
+}

recipes-kernel/linux-rt/rt.inc

@@ -0,0 +1,2 @@
+RT_PATCH_URI = "https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patch-5.10.35-rt39.patch.xz;sha256sum=3e1d3531173d5bb276935eaec016ef3c3c0f8f4fcc1fc418d192cc10824ff80d"
+

templates/local.conf/rt_kernel.append

@@ -0,0 +1,3 @@
+#;prompt Realtime kernel support [no]
+
+IMAGE_FEATURES += " realtime-kernel "