I have tried to convert my existing ndk Project to Android Studio according to http://ph0b.com/new-android-studio-ndk-support/#usingndkbuild but couldn't resolve all errors.
Now I get following error:
/home/nxp/Documents/Projects/Android_Ucode_demo/app/src/main/jni/ECDSA-jni.c 
Error:(44, 30) openssl/ossl_typ.h: No such file or directory
Folder Structure:
app
  build
    ...
  libs
    ...
  src
    main
      assets
        ...
      java
        ...
      jni
        include.openssl
          ...
          ossl_type.h
          ...
        Android.mk
        libcrypto-static.a
        ECDSA-jni.c
      jniLibs
        armeabi
          libECDSA.so
      res
        ...
      AndroidManifest
    app.iml
    build.gradle
    lint.xml
build
  ...
gradle
  ...
...
build.gradle
...
build.gradle
buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        //classpath 'com.android.tools.build:gradle:1.3.0'
        classpath 'com.android.tools.build:gradle-experimental:0.2.0'
    }
}
allprojects {
    repositories {
        jcenter()
    }
}
gradle/wrapper/gradle-wrapper.properties
#Thu Sep 17 09:57:00 CEST 2015
distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-2.5-all.zip
app/build.gradle
apply plugin: 'com.android.model.application'
model {
    android {
        compileSdkVersion = 22
        buildToolsVersion = "23.0.1"
        defaultConfig.with {
            applicationId = "com.mycompany.myapp"
            minSdkVersion.apiLevel = 15
            targetSdkVersion.apiLevel = 22
        }
    }
    android.ndk {
        moduleName = "openssl"
    }
    android.sources{
        main.jni {
            source {
                srcDirs = ['src/main/jni']
            }
        }
        main.jniLibs {
            source {
                srcDirs = ['src/main/jniLibs']
            }
        }
    }
    android.buildTypes {
        release {
            minifyEnabled = false
            proguardFiles += file('proguard-rules.txt')
        }
    }
}
dependencies {
    compile 'com.android.support:support-v4:22.0.0'
    compile files('libs/aretepoplib.jar')
}
app/src/main/jni/Android.mk
LOCAL_PATH := $(call my-dir)
$(info LOCAL_PATH := $(LOCAL_PATH))
include $(CLEAR_VARS)
LOCAL_MODULE := openssl
LOCAL_SRC_FILES = libcrypto-static.a
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_C_INCLUDES:= $(LOCAL_PATH)/include frameworks/base/include 
LOCAL_LDLIBS    := -llog -lGLESv2
LOCAL_MODULE    := ECDSA
LOCAL_SRC_FILES := ECDSA-jni.c
LOCAL_STATIC_LIBRARIES := openssl
include $(BUILD_SHARED_LIBRARY)